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  • 1.
    Ahlström, Peter
    et al.
    University of Borås, School of Engineering.
    Gebäck, Tobias
    University of Borås, School of Engineering.
    Johansson, Erik
    University of Borås, School of Engineering.
    Bolton, Kim
    University of Borås, School of Engineering.
    Water absorption in polymers2010Conference paper (Other academic)
    Abstract [en]

    In this work two different examples of water absorbtion in polymers are studied by Monte Carlo simulations. Both of them are of large technical and commercial impotance. The first example is the water absorption in polyethylene cables where the water absorption plays a crucial role in the degradation of the cable insulation and thus should be as low as possible. The second example is bio-based superabsorbents made from denatured protein where water absorption capability is the prime desired property. Methods Gibbs Ensemble Monte Carlo simulations [1] were used to study the hydration of polymers. All simulations are performed with two boxes, one of which is filled with water at the start of the simulation, whereas the other contains polymer molecules and possible ions. The polymer molecules are not allowed to swap boxes whereas the water molecules are allowed to do so thus constituting an osmotic Gibbs ensemble [2]. For the polyethylene a connectivity-altering algorithm was used whereas the protein molecules were simulated using a side-chain regrowth model in addition to traditional Monte Carlo moves. For the polyethylene, the TraPPE [3] force field was used and the protein molecules, the Amber force field [4] was used. Water was modelled using simple point charge models [5]. Electrostatic interactions are treated using Ewald summation methods. The protein molecules were of different amino acid compositions and in different conformations, e.g., β-turns and random coils obtained using the amorphous cell method[6]. Studies were made with different degrees of charging on, e.g., lysine side chains mimicking different ionization states. Results The studies of polyethylene revealed the importance of ions left from the polymerisation catalyst for the absorbtion of water and the concomitant degradation of polyethylene cable insulation. Also the absorption properties of the protein molecules is strongly related to the presence of charged groups and fully charged protein molecules absorb large amounts of water. However, neither native nor denatured protein molecules show superabsorbing properties (i.e. absorbing hundreds of times their own mass) as they show in experimental studies and the reasons for this discrepancy will be discussed. References 1. A.Z. Panagiotopoulos, Mol. Phys. 61, 813 (1987). 2. E. Johansson, K. Bolton, D.N. Theodorou, P. Ahlström, J. Chem. Phys., 126, 224902 (2007). 3. M.G. Martin, and J.I. Siepmann, J. Phys. Chem. B, 103, 4508-4517 (1999). 4. W.D. Cornell, P. Cieplak, C.I. Bayly, I.R. Gould, K.M. Merz Jr, D.M. Ferguson, D.C. Spellmeyer, T. Fox, J.W. Caldwell, P.A. Kollman (1995). J. Am. Chem. Soc. 117, 5179–5197. 5. H. J. C. Berendsen, J. P. M. Postma and W. F. van Gunsteren, in Intermolecular Forces, B. Pullman, ed. (Reidel, Dordrecht, 1981) p. 331; H. J. C. Berendsen, J. R. Grigera and T. P. Straatsma, J. Phys. Chem. 91, 6269 (1987). 6. D.N. Theodorou, U.W. Suter, Macromolecules, 18, 1467 (1985).

  • 2.
    Ahlström, Peter
    et al.
    University of Borås, School of Engineering.
    Moodley, Suren
    University of Borås, School of Engineering.
    Bolton, Kim
    University of Borås, School of Engineering.
    Ramjugernath, D.
    University of Borås, School of Engineering.
    Computer Simulations of Vapor-Liquid-Liquid Equilibria Involving Hydrocarbons and Water2008In: Proceedings of the 100th Annual Meeting of the American Institute for Chemical Engineering, 2008, CHPC National Meeting, Durban, South Africa, December 9-10, 2008, AlChe Annual Meeting, Philadelphia, November 15-21, 2008, 2008Conference paper (Other academic)
  • 3.
    Arja, Mina
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Akbar Mirzaei, Ali
    University of Sistan and Baluchestan, Zahedan 98135-674, Iran.
    Mahmood Davarpanah, Abdol
    University of Sistan and Baluchestan, Zahedan 98135-674, Iran.
    Masoud Barakati, Seyed
    University of Sistan and Baluchestan, Zahedan 98135-674, Iran.
    Mohsenzadeh, Abas
    University of Borås, Faculty of Textiles, Engineering and Business.
    Atashi, Hossein
    University of Sistan and Baluchestan, Zahedan 98135-674, Iran.
    Bolton, Kim
    University of Borås, Faculty of Textiles, Engineering and Business.
    DFT studies of hydrocarbon combustion on metal surfaces2018In: Journal of Molecular Modeling, ISSN 1610-2940, E-ISSN 0948-5023, Vol. 24, p. 47-Article in journal (Refereed)
  • 4.
    Bazooyar, Faranak
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Bohlén, Martin
    University of Borås, Faculty of Textiles, Engineering and Business.
    Bolton, Kim
    University of Borås, Faculty of Textiles, Engineering and Business.
    Computational Studies of Water and Carbon Dioxide Interactions with Cellobiose2015In: Journal of Molecular Modeling, ISSN 1610-2940, E-ISSN 0948-5023, Vol. 21, p. 2553-Article in journal (Refereed)
    Abstract [en]

    B3LYP/6-311++G** with dispersion correction (DFT-D) was used to study local and global minimum energy structures of water (H2O) or carbon dioxide (CO2) bonding with a pair of cellobiose molecules. The calculations showed that neither the H2O nor the CO2 prefer to be between the cellobiose molecules, and that the minimum energy structures occur when these molecules bond to the outer surface of the cellobiose pair. The calculations also showed that the low energy structures have a larger number of inter-cellobiose hydrogen bonds than the high energy structures. These results indicate that penetration of H2O or CO2 between adjacent cellobiose pairs, which would assist steam or supercritical CO2 (SC-CO2) explosion of cellulose, is not energetically favored. Comparison of the energies obtained with DFT-D and DFT (the same method but without dispersion correction) show that both hydrogen bonds and van der Waals interactions play an important role in cellobiose-cellobiose interactions.

  • 5.
    Bazooyar, Faranak
    et al.
    University of Borås, School of Engineering.
    Bolton, Kim
    University of Borås, School of Engineering.
    Molecular-level Simulations of Cellulose Dissolution by Steam and SC-CO2 Explosion2014Conference paper (Refereed)
    Abstract [en]

    Dissolution of cellulose is an important but tough step in biofuel production from lignocellulosic materials. Steam and supercritical carbon dioxide (SC-CO2) explosion are two effective methods for dissolution of some lignocellulosic materials. Loading and explosion are the major processes of these methods. Studies of these processes were performed using grand canonical Monte Carlo and molecular dynamics simulations at different pressure/ temperature conditions on the crystalline structure of cellulose. The COMPASS force field was used for both methods. The validity of the COMPASS force field for the calculations was confirmed by comparing the energy and structures obtained from molecular mechanics simulations of cellobiose (the repeat unit of cellulose), water–cellobiose, water-cellobiose pair and CO2-cellobiose pair systems with those obtained from first principle calculations with and without dispersion correction. A larger disruption of the cellulose crystal structure was seen during loading than that during the explosion process. This is seen by an increased separation of the cellulose chains from the centre of mass of the crystal during the initial stages of the loading, especially for chains in the outer shell of the crystalline structure. Reducing and non-reducing ends of the cellulose crystal show larger disruption than the central core; this leads to increasing susceptibility to enzymatic attack in these end regions. There was also change from the syn to the anti torsion angle conformations, especially for chains in the outer cellulose shell. Increasing the temperature increases the disruption of the crystalline structure during loading and explosion.

  • 6.
    Bazooyar, Faranak
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Bolton, Kim
    University of Borås, Faculty of Textiles, Engineering and Business.
    Molecular-level Simulations of Cellulose Steam Explosion2015In: Quantum Matter, ISSN 2164-7615, Vol. 4, no 2, p. 115-122Article in journal (Refereed)
    Abstract [en]

    Grand canonical Monte Carlo and molecular dynamics simulations are used to study steam explosion of crystalline cellulose using 100, 160, 210 and 250 °C saturated steam. The simulations are based on the COMPASS force field, which provides a valid description of the cellulose crystal structure and water-cellobiose interactions. Disruption of the crystal structure during steaming is typically larger than that during the explosion stage and the restructuring is larger at increased temperature and pressure. This is seen by an increased separation of the cellulose chains from the center of mass of the crystal during the initial stages of the steaming, especially for chains in the outer shell of the elementary fibril. There is a large change in the radius of gyration and fraction of anti torsion angle conformers for chains in the outer shell of the elementary fibril. In addition, the disruption at the reducing and non-reducing ends of the cellulose crystal is larger than in the central core, increasing susceptibility to enzymatic attack in these end regions.

  • 7.
    Bazooyar, Faranak
    et al.
    University of Borås, School of Engineering.
    Momany, Frank A.
    Bolton, Kim
    University of Borås, School of Engineering.
    Validating Empirical Force Fields for Molecular-level Simulation of Cellulose Dissolution2012In: Computational and Theoretical Chemistry, ISSN 2210-271X, E-ISSN 2210-2728, Vol. 984, p. 119-127Article in journal (Refereed)
    Abstract [en]

    The calculations presented here, which include dynamics simulations using molecular mechanics forcefields and first principles studies, indicate that the COMPASS forcefield is preferred over the Dreiding and Universal forcefields for studying dissolution of large cellulose structures. The validity of these forcefields was assessed by comparing structures and energies of cellobiose, which is the shortest cellulose chain, obtained from the forcefields with those obtained from MP2 and DFT methods. In agreement with the first principles methods, COMPASS is the only forcefield of the three studied here that favors the anti form of cellobiose in the vacuum. This forcefield was also used to compare changes in energies when hydrating cellobiose with 1–4 water molecules. Although the COMPASS forcefield does not yield the change from anti to syn minimum energy structure when hydrating with more than two water molecules – as predicted by DFT – it does predict that the syn conformer is preferred when simulating cellobiose in bulk liquid water and at temperatures relevant to cellulosedissolution. This indicates that the COMPASS forcefield yields valid structures of cellulose under these conditions. Simulations based on the COMPASS forcefield show that, due to entropic effects, the syn form of cellobiose is energetically preferred at elevated temperature, both in vacuum and in bulk water. This is also in agreement with DFT calculations.

  • 8. Bazooyar, Faranak
    et al.
    Taherzadeh, M.J.
    University of Borås, School of Engineering.
    Niklasson, C.
    Bolton, K.
    University of Borås, School of Engineering.
    Molecular modeling of cellulose dissolution2013In: Journal of Computational and Theoretical Nanoscience, ISSN 1546-1955, E-ISSN 1546-1963, Vol. 10, no 11, p. 2639-2648Article in journal (Refereed)
    Abstract [en]

    In this work we present computational studies that shed light on the molecular mechanism of the initial stages of cellulose dissolution in saturated steam, which is an important pretreatment step in the conversion of lignocellulose to biofuel. The COMPASS, Dreiding and Universal molecular mechanics force fields and the B3LYP density functional with 6-311G, 6-311++G(d,p) and 6-311++G(2d,2p) basis sets were used to study systems containing glucose, cellobiose and water. These molecular systems were studied since they are sufficiently small to perform the density functional theory calculations in a tractable time, while also being relevant to the dissolution of cellulose in saturated steam. Comparison of the energies and structures obtained from the three force fields with those obtained from the first principles method showed that the COMPASS force field is preferred to the other two and that this force field gives similar structures obtained from the first principles method. This supports the validity of the COMPASS force field for studying cellulose dissolution in saturated steam, and preliminary simulations were performed using grand canonical Monte Carlo and molecular dynamics simulations of cellulose dissolution in saturated steam at 100 °C and 1 bar, 160 °C and 6.2 bar, and 250 °C and 39.7 bar. The results show that the cellulose crystal dissolves in saturated steam at the higher temperatures and pressures.

  • 9.
    Björk, Hans
    et al.
    University of Borås, School of Engineering.
    Lindecrantz, Kaj
    University of Borås, School of Engineering.
    Ericsson, Dag
    University of Borås, School of Engineering.
    Sarv, Hans
    University of Borås, School of Engineering.
    Bolton, Kim
    University of Borås, School of Engineering.
    Börjesson, Anders
    University of Borås, School of Engineering.
    Bazooyar, Faranak
    University of Borås, School of Engineering.
    Ahlström, Peter
    University of Borås, School of Engineering.
    Taherzadeh, Mohammad
    University of Borås, School of Engineering.
    Andersson, Bengt-Åke
    University of Borås, School of Engineering.
    Johansson, Andreas
    University of Borås, School of Engineering.
    Skrifvars, Mikael
    University of Borås, School of Engineering.
    20 år med Institutionen Ingenjörshögskolan: historik, nuläge och framtid2009Report (Other academic)
  • 10.
    Bohlén, Martin
    et al.
    University of Borås, School of Engineering.
    Bolton, Kim
    University of Borås, School of Engineering.
    Conformational studies of poly(vinylidene fluoride), poly(trifluoroethylene) and poly(vinylidene fluoride-co-trifluoroethylene) using density functional theory2014In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 25, p. 12929-12939Article in journal (Refereed)
    Abstract [en]

    Different conformations of systems consisting of poly(vinylidene fluoride) (PVDF), poly(trifluoroethylene) (PTrFE) and poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) were investigated using density functional theory with dispersion correction. It was found that the trans-gauche-trans-gauche´ (TGTG´) conformation of a single PVDF chain is the lowest energy conformer. Crystals of PVDF were modelled using between two to five chains with up to 12 repeat units in each chain and, in agreement with experiment, structures comprised partly or completely of chains with the TGTG´ conformation are more stable than structures built up from chains with all-trans (TTTT) conformation. This indicates that an all-trans segment or chain will not induce the growth of a larger crystal with the same chain conformations. In contrast, the energetically preferred structure of PTrFE chains is an all-trans (TTTT) conformation, and the results indicate that copolymerization of vinylidene fluoride with trifluoroethylene can facilitate the formation of the all-trans PVDF conformations. This is probably due to increased intramolecular repulsion between the fluorine atoms and an increased intermolecular attraction in the crystal structure.

  • 11.
    Bohlén, Martin
    et al.
    University of Borås, School of Engineering.
    Bolton, Kim
    University of Borås, School of Engineering.
    Effect of single wall carbon nanotubes on the conformation of Poly(vinylidene fluoride)2014In: Quantum Matter, ISSN 2164-7615, Vol. 3, no 4, p. 339-343Article in journal (Refereed)
    Abstract [en]

    Structures consisting of single Poly(vinylidene fluoride) (PVDF) chains, single wall carbon nanotubes (SWCNTs), a PVDF chain interacting with a SWCNT and of five PVDF chains arranged to resemble the α and β crystal structures of PVDF were evaluated using geometry optimizations and single point energy calculations. Density functional theory with dispersion correction was used for all calculations. The conformer of PVDF is the lowest energy structure, irrespective of whether the SWCNT is present or not. Interaction with the SWCNT reduces the energy difference between the β and α conformers by approximately 30%, indicating that SWCNTs can increase the relative amount of the β conformers at higher temperatures. However, even in the presence of the SWCNT this energy difference is approximately 1.67 kcal/mol per –CH2CF2– repeat unit, which is larger than kT at 300 K (0.6 kcal/mol). Hence, the presence of the SWCNTs is not expected to substantially increase the relative amount of the β conformers at these conditions. Compression of the α and β crystal structures, which occurs during fibre extrusion, and which may be increased if nanoparticles are present in the polymer matrix, further decreases the energy difference between the β and α conformers but only to a very small extent at pressures relevant to fibre extrusion.

  • 12.
    Bohlén, Martin
    et al.
    University of Borås, School of Engineering.
    Bolton, Kim
    University of Borås, School of Engineering.
    Inducing the piezoelectric β-phase of PVDF: a DFT study2014Conference paper (Refereed)
  • 13.
    Bohlén, Martin
    et al.
    University of Borås, School of Engineering.
    Bolton, Kim
    University of Borås, School of Engineering.
    Inducing the β-phase of poly(vinylidene fluoride): a review2014In: Annual Review of Nanoscience and Nanotechnology, ISSN 2159-9688, Vol. 1, no 1Article in journal (Refereed)
    Abstract [en]

    Poly(vinylidene fluoride) (PVDF) is a versatile material with numerous applications in many fields of industry and science. The extent of applications, ranging from approved contact materials in the food industry to monitors for respiration and heart-rate in medicine, drives the research and development by the materials science community. The largest limiting factor when using PVDF in applications where its piezo- and pyroelectricity is important, is the amount of the highly polar crystalline β-phase in the material. PVDF is polymorphic and usually crystallizes from melt or solution into the non-polar α-phase, which is of little use in piezoelectric applications. Many studies have therefore aimed at increasing the amount of the β-phase crystal structure in the material. Cold drawing of α-phase PVDF, poling in high electric fields, copolymerization with trifluoroethylene, and inclusion of different types of additives to PVDF have been studied using both experimental and computational techniques. This review presents the current status and understanding of these processes, and summarizes results from previous studies. © Global Scientific Publishers 2015.

  • 14.
    Bohlén, Martin
    et al.
    University of Borås, School of Engineering.
    Bolton, Kim
    University of Borås, School of Engineering.
    Molecular Dynamics Studies of the Influence of Single Wall Carbon Nanotubes on the Mechanical Properties of Poly(vinylidene fluoride)2013In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 68, p. 73-80Article in journal (Refereed)
    Abstract [en]

    Molecular dynamics simulations and geometry optimizations based on the Condensed-phase Optimized Molecular Potentials for Atomistic Simulation Studies (COMPASS) force field were performed to understand the effect of Single Wall Carbon Nanotubes (SWCNTs) on the mechanical properties of Poly(vinylidene fluoride) (PVDF). In particular, the Young’s modulus, bulk and shear modulus, pullout energy, pullout force, interfacial shear stress and interfacial bonding energy were calculated. The presence of the SWCNTs can increase the Young’s modulus of the systems studied here by 1 GPa in the direction of the SWCNT axis, although this depends on the distance between neighboring SWCNTs. The calculated interfacial shear stress was between 100 and 129 MPa, which is in agreement with results obtained for other SWCNT-polymer systems. The results, and in particular those obtained for the bulk and shear modulus, show that SWCNTs do not have a significant effect on the bulk mechanical properties. Functionalizing the SWCNTs may yield stronger adhesion between the nanotube and the polymer, thereby achieving improved mechanical properties. ⺠Computational studies using molecular dynamics and molecular mechanics. ⺠Effect of single wall carbon nanotubes on the mechanical properties of Poly(vinylidene fluoride). ⺠Alignment of the nanotubes plays a crucial role for the reinforcing effect. ⺠When aligned, an increase in Young’s modulus of approximately 1 GPa could be observed. ⺠The interfacial shear stress was calculated to be in the range of 100–129 MPa.

  • 15.
    Bohlén, Martin
    et al.
    University of Borås, School of Engineering.
    Satyanarayana, Kavitha Chelakara
    Bolton, Kim
    University of Borås, School of Engineering.
    Computational Studies of Poly(vinylidene fluoride)-Single Wall Carbon Nanotube Systems2013In: Journal of Computational and Theoretical Nanoscience, ISSN 1546-1955, E-ISSN 1546-1963, Vol. 10, no 6, p. 1317-1325Article in journal (Refereed)
    Abstract [en]

    First principles and molecular mechanics methods have been used to study poly(vinylidene fluoride)—single wall carbon nanotube systems. First principles calculations (Møller-Plesset second order perturbation theory and density functional theory with B3LYP exchange correlation functional with and without dispersion correction) using short poly(vinylidene fluoride) segments and short hydrogen-capped single wall carbon nanotubes show that the polymer segments prefer to have the β-rather than the β-conformation both in the absence and presence of the single wall carbon nanotube. The lowest energy structure is obtained when the poly(vinylidene fluoride) has an β-conformation and is located parallel to the single wall carbon nanotube wall. In contrast to the Dreiding and Universal force fields, the COMPASS force field predicts the structures containing the β-conformation of poly(vinylidene fluoride) to be the lowest in energy in agreement with first principles results. The COMPASS force field was consequently used in preliminary studies of a longer poly(vinylidene fluoride) chain and a longer single wall carbon nanotube using molecular dynamics.

  • 16.
    Bolton, Kim
    University of Borås, School of Engineering.
    Modelling carbon nanotube growth2008Conference paper (Other academic)
  • 17.
    Bolton, Kim
    University of Borås, School of Engineering.
    Simulations of water, metal and carbon clustering2008Conference paper (Other academic)
  • 18.
    Bolton, Kim
    et al.
    University of Borås, School of Engineering.
    Börjesson, Anders
    University of Borås, School of Engineering.
    Computational studies of single-walled carbon nanotube growth2011In: SNIC Progress Report (2008-2009), p. 40-46Article in journal (Other academic)
    Abstract [en]

    Allocation of time on the Swedish national supercomputing facilities since 2000, as well as support from other sources, has allowed us to perform computational studies on a wide variety of systems. These include properties and growth of carbon nanotubes [1–36], icecatalysed reactions of importance to stratospheric ozone depletion[37], calculations of vapour-liquid, liquid-liquid and vapour-liquid-liquid phase equilibrium of single, binary and ternary component systems[38], and, more recently, carbonaceous polymer nanocomposites and cellulose decomposition. More details of these projects are available at the web page given above.

  • 19.
    Bolton, Kim
    et al.
    University of Borås, School of Engineering.
    Börjesson, Anders
    University of Borås, School of Engineering.
    Ahlström, Peter
    University of Borås, School of Engineering.
    Bazooyar, Faranak
    University of Borås, School of Engineering.
    Beräkningsteknik2009In: Vetenskap för profession, ISSN 1654-6520, no 10, p. 63-68Article in journal (Other academic)
  • 20.
    Bolton, Kim
    et al.
    University of Borås, School of Engineering.
    Börjesson, Anders
    University of Borås, School of Engineering.
    Zhu, Wuming
    Amara, Hakim
    Bichara, Christophe
    Density functional theory and tight binding-based dynamical studies of carbon metal systems of relevance to carbon nanotube growth2009In: Nano Reseach, ISSN 1998-0124, E-ISSN 1998-0000, Vol. 2, no 10, p. 774-782Article in journal (Refereed)
    Abstract [en]

    Density functional theory (DFT) and tight binding (TB) models have been used to study systems containing single-walled carbon nanotubes (SWNTs) and metal clusters that are of relevance to SWNT growth and regrowth. In particular, TB-based Monte Carlo (TBMC) simulations at 1000 or 1500 K show that Ni atoms that are initially on the surface of the SWNT or that are clustered near the SWNT end diffuse to the nanotube end so that virtually none of the Ni atoms are located inside the nanotube. This occurs, in part, due to the lowering of the Ni atom energies when they retract from the SWNT to the interior of the cluster. Aggregation of the atoms at the SWNT end does not change the chirality within the simulation time, which supports the application of SWNT regrowth (seeded growth) as a potential route for chirality-controlled SWNT production. DFT-based geometry optimisation and direct dynamics at 2000 K show that Cr and Mo atoms in Cr5Co50 and Mo5Co50 clusters prefer to be distributed in the interior of the clusters. Extension of these calculations should deepen our understanding of the role of the various alloy components in SWNT growth.

  • 21.
    Bolton, Kim
    et al.
    University of Borås, School of Engineering.
    Christie, Michael
    Ingerman, Åke
    Linder, Cedric
    Saalman, Elisabeth
    SimChemistry as an active learning tool in chemical education2008In: Chemistry Education Research and Practice, ISSN 1756-1108, E-ISSN 1756-1108, Vol. 9, no 3, p. 277-284Article in journal (Refereed)
    Abstract [en]

    The publicly available free computer program, SimChemistry, was used as an active learning tool in the chemical engineering curriculum at the University College of Borås, Sweden. The activity involved students writing their own simulation programs on topics in the area of molecular structure and interactions. Evaluation of the learning experience was done using interviews and by comparing learning outcomes with previous teachings of the topics. Overall, the outcome was interactively engaging group work, high quality construction of simulations, and a much better ability to explain molecular-level chemical concepts and their relations. An interesting perception that emerged during the interviews was that many of the students were unable to explicitly describe the improvement in learning that they had experienced. However, they did recognize that learning had occurred, and all firmly and positively recommended that the initiative be continued for subsequent courses.

  • 22.
    Bolton, Kim
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    De Mena, Barbara
    ttz Bremerhaven.
    Schories, Gerhard
    ttz Bremerhaven.
    Sustainable Management of Solid Waste2016In: Resource Recovery to approach zero municipal wastes / [ed] M. J. Taherzadeh and T. Richards, CRC Press, 2016, p. 23-41Chapter in book (Refereed)
  • 23.
    Bolton, Kim
    et al.
    University of Borås, School of Engineering.
    Ding, F.
    Börjesson, Arne
    Zhu, W.M.
    Duan, H.M.
    Harutyunyan, A.R.
    Curtarlo, S.
    Computational Studies of Catalytic Particles for Carbon Nanotube Growth2009In: Journal of Computational and Theoretical Nanoscience, ISSN 1546-1955, E-ISSN 1546-1963, Vol. 6, no 1, p. 1-15Article in journal (Refereed)
    Abstract [en]

    We review our computational studies of the melting temperatures and mechanisms of iron and iron-carbide clusters. Both isolated and supported clusters have been considered, and substrates with different shapes or pores have been simulated. It has been seen, for example, that the surface curvature—or local surface curvature—of the particle plays a dominant role in the melting mechanism and temperature. It has also been observed that the melting mechanism for small clusters is different to that of larger clusters.

  • 24.
    Bolton, Kim
    et al.
    University of Borås, School of Engineering.
    Johansson, Erik
    University of Borås, School of Engineering.
    Jönsson, Lennart
    University of Borås, School of Engineering.
    Ahlström, Peter
    University of Borås, School of Engineering.
    Simulation of water clusters in vapour, alkanes and polyethylenes2009In: Molecular Simulation, ISSN 0892-7022, E-ISSN 1029-0435, Vol. 35, no 10/11, p. 888-896Article in journal (Refereed)
    Abstract [en]

    The Gibbs Ensemble Monte Carlo (GEMC) technique has been used to study the clustering of water in vapour, alkanes and polyethylene, where the water clusters are in equilibrium with liquid phase water. The effect of an external electric field and ionic impurities on the clustering of water in the hydrocarbons (alkanes and polyethylene) has also been studied. The simulations of water clustering in polyethylene were made more efficient by using a connectivity altering osmotic Gibbs ensemble method. It was found that trends in the size distribution of water clusters in the hydrocarbons are similar to those found in the pure vapour, but that fewer and smaller clusters are formed as the length of the hydrocarbon chain increased. Also, large external electric fields decrease the solubility of water in hydrocarbons, whereas the presence of ionic species dramatically increases the solubility.

  • 25.
    Bolton, Kim
    et al.
    University of Borås, School of Engineering.
    Richards, Tobias
    University of Borås, School of Engineering.
    Mohsenzadeh Syouki, Abas
    University of Borås, School of Engineering.
    DFT study of the adsorption and dissociation of water on Ni(111), Ni(110) and Ni(100) surfaces2014In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 627, p. 1-10Article in journal (Refereed)
    Abstract [en]

    Water adsorption and dissociation on catalytic metal surfaces play a key role in a variety of industrial processes, and a detailed understanding of this process and how it is effected by the surface structure will assist in developing improved catalysts. Hence, a comparative study of the adsorption and dissociation of water on Ni(111), Ni(110) and Ni(100) surfaces, which is often used as catalyst, has been performed using density functional theory. The results show that the adsorption energies and dissociation rates depend on the surface structure. The adsorption energies for H2O and OH decrease in the order Ni(110) > Ni(100) > Ni(111), and for the O and H atoms the adsorption energies decrease in the order Ni(100) > Ni(111) > Ni(110). In addition, the splitting of water to OH and H has lower activation energies over less packed Ni(110) and Ni(100) surfaces compared to the highly packed Ni(111) surface. The subsequent splitting of the OH to O and H also has the lowest activation energy on the Ni(110) surface. At 463 K, which is typical for industrial processes that include the water gas shift reaction, the H2O splitting is approximately 6000 and 10 times faster on the Ni(110) surface compared to the Ni(111) and Ni(100) surfaces, respectively, and OH splitting is 200 and 3000 times faster, respectively. The complete water dissociation reaction rate decreases in the order Ni(110) > Ni(100) > Ni(111).

  • 26.
    Bolton, Kim
    et al.
    University of Borås, School of Engineering.
    Zhu, Wuming
    Börjesson, Anders
    Progress in understanding controlled single-wall carbon nanotube growth from computer simulations2012In: Journal of Computational and Theoretical Nanoscience, ISSN 1546-1955, E-ISSN 1546-1963, Vol. 9, no 6, p. 819-825Article in journal (Refereed)
    Abstract [en]

    Density functional theory based on the PW91 and PBE exchange-correlation functionals was used to study processes that are expected to play a key role in single-walled carbon nanotube (SWNT) growth and continued growth. It is shown that Ni clusters adapt their shape to the shape of the SWNT end to which they are attached. The results also show that the presence of SWNTs affects Ostwald ripening of the catalyst metal clusters and that, under certain conditions, the net diffusion may be from larger to smaller clusters. Also, Ostwald ripening may affect the chiral distribution of the SWNTs.

  • 27.
    Brancoli, Pedro
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business. University of Borås.
    Bolton, Kim
    University of Borås, Faculty of Textiles, Engineering and Business.
    Rousta, Kamran
    University of Borås, Faculty of Textiles, Engineering and Business.
    LCA as a Supporting Tool for Supermarket Food Waste Management2016Conference paper (Other academic)
  • 28.
    Brancoli, Pedro
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Bolton, Kim
    University of Borås, Faculty of Textiles, Engineering and Business.
    Rousta, Kamran
    University of Borås, Faculty of Textiles, Engineering and Business.
    Life cycle assessment of supermarket food waste2017In: Resources, Conservation and Recycling, ISSN 0921-3449, E-ISSN 1879-0658, Vol. 118, p. 39-46Article in journal (Refereed)
    Abstract [en]

    Retail is an important actor regarding waste throughout the entire food supply chain. Although it produces lower amounts of waste compared to other steps in the food value chain, such as households and agriculture, it has a significant influence on the supply chain, including both suppliers in the upstream processes and consumers in the downstream. The research presented in this contribution analyses the impacts of food waste at a supermarket in Sweden. In addition to shedding light on which waste fractions have the largest environmental impacts and what part of the waste life cycle is responsible for the majority of the impacts, the results provide information to support development of strategies and actions to reduce of the supermarket's environmental footprint. Therefore, the food waste was categorised and quantified over the period of one year, the environmental impacts of waste that were generated regularly and in large amounts were assessed, and alternative waste management practices were suggested. The research revealed the importance of not only measuring the food waste in terms of mass, but also in terms of environmental impacts and economic costs. The results show that meat and bread waste contributes the most to the environmental footprint of the supermarket. Since bread is a large fraction of the food waste for many Swedish supermarkets, this is a key item for actions aimed at reducing the environmental footprint of supermarkets. Separation of waste packaging from its food content at the source and the use of bread as animal feed were investigated as alternative waste treatment routes and the results show that both have the potential to lead to a reduction in the carbon footprint of the supermarket.

  • 29.
    Brancoli, Pedro
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Ferreira, Jorge A.
    University of Borås, Faculty of Textiles, Engineering and Business.
    Bolton, Kim
    University of Borås, Faculty of Textiles, Engineering and Business.
    Taherzadeh, Mohammad J
    University of Borås, Faculty of Textiles, Engineering and Business.
    Changes in carbon footprint when integrating production of filamentous fungi in 1st generation ethanol plants2017In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976Article in journal (Refereed)
    Abstract [en]

    Integrating the cultivation of edible filamentous fungi in the thin stillage from ethanol production is presently being considered. This integration can increase the ethanol yield while simultaneously producing a new value-added protein-rich biomass that can be used for animal feed. This study uses life cycle assessment to determine the change in greenhouse gas (GHG) emissions when integrating the cultivation of filamentous fungi in ethanol production. The result shows that the integration performs better than the current scenario when the fungal biomass is used as cattle feed for system expansion and when energy allocation is used. It performs worse if the biomass is used as fish feed. Hence, integrating the cultivation of filamentous fungi in 1st generation ethanol plants combined with proper use of the fungi can lead to a reduction of GHG emissions which, considering the number of existing ethanol plants, can have a significant global impact.

  • 30.
    Brancoli, Pedro
    et al.
    University of Borås, Faculty of Textiles, Engineering and Business. University of Borås.
    Rousta, Kamran
    University of Borås, Faculty of Textiles, Engineering and Business.
    Bolton, Kim
    University of Borås, Faculty of Textiles, Engineering and Business.
    Environmental impacts of supermarket food waste in a life cycle perspective2016Conference paper (Other academic)
  • 31.
    Börjesson, A.
    et al.
    University of Borås, School of Engineering.
    Zhu, W.
    Amara, H.
    Bichara, C.
    Ducastelle, F.
    Bolton, Kim
    University of Borås, School of Engineering.
    Theoretical investigation of the Nanotube-metal junction2008Conference paper (Other academic)
  • 32.
    Börjesson, Anders
    et al.
    University of Borås, School of Engineering.
    Bolton, Kim
    University of Borås, School of Engineering.
    First Principles Studies of the Effect of Nickel Carbide Catalyst Composition on Carbon Nanotube Growth2010In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, no 42, p. 18045-18050Article in journal (Refereed)
    Abstract [en]

    Density functional theory calculations were used to investigate the stability of single-walled carbon nanotubes (CNTs) attached to nanoparticles. The total energies and the adhesion energies between the CNTs and the nanoparticles were calculated for systems where the nanoparticles were either pure Ni or Ni carbide. It was found that the adhesion between the CNT and a pure Ni cluster is stronger than between the same CNT and a Ni carbide cluster although the energy difference was small compared to the total adhesion energies. This adhesion strength implies that CNTs are likely to remain attached to both pure Ni and Ni carbide clusters and that either pure Ni or Ni carbide clusters may be docked onto the open CNT ends to achieve continued growth or electronic contacts between CNTs and electrode materials. The system with a CNT attached to a pure Ni cluster was found to be energetically favored compared to a system containing the same CNT attached to a Ni carbide. The difference in total energy implies that a CNT should act as a sink for C atoms dissolved in the Ni carbide cluster, which means that the dissolved C atoms will be drained from the cluster, yielding a pure metal in the zero Kelvin thermodynamic limit. It is argued that this draining procedure is likely to occur even if carbon is added to the cluster at a proper rate, for example, during CNT growth.

  • 33.
    Börjesson, Anders
    et al.
    University of Borås, School of Engineering.
    Bolton, Kim
    University of Borås, School of Engineering.
    First Principles Studies of the Effect of Ostwald Ripening on Carbon Nanotube Chirality Distributions2011In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 5, no 2, p. 771-779Article in journal (Refereed)
    Abstract [en]

    The effect of Ostwald ripening of metal particles attached to carbon nanotubes has been studied using density functional theory. It has been confirmed that Ostwald ripening may be responsible for the termination of growth of carbon nanotube forests. It was seen that the Ostwald ripening of metal particles attached to carbon nanotubes is governed by a critical factor that depends on both the cluster size and the carbon nanotube chirality. For example, clusters attached to armchair and zigzag nanotubes of similar diameters will have different critical factors although the exact behavior may depend on which molecules are present in the surrounding medium. The critical factor was also observed to have a critical point with the effect that clusters with a narrow size distribution close to the critical point may experience a narrowing rather than a widening of the size distribution, as is the case for free clusters.

  • 34.
    Börjesson, Anders
    et al.
    University of Borås, School of Engineering.
    Bolton, Kim
    University of Borås, School of Engineering. University of Borås, Swedish School of Textiles.
    Modelling of Ostwald ripening of metal clusters attached to carbon nanotubes2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 50, p. 24454-24462Article in journal (Refereed)
    Abstract [en]

    We present a model of Ostwald ripening of nanosized clusters and apply it to study the time evolution of metal particles attached to carbon nanotubes. The Ostwald ripening of metal clusters attached to carbon nanotubes differs from that of free metal clusters. While free clusters experience a rapid broadening in the size dispersion, this may be delayed by the nanotubes, which may therefore limit the ripening. The diameter and chirality of the carbon nanotubes were also seen to affect the Ostwald ripening of the catalyst particles. For a collection of carbon nanotubes that contains different diameters and chiralities, the clusters attached to carbon nanotubes with large diameters and strong carbon–metal adhesion are the most likely to survive the Ostwald ripening.

  • 35.
    Börjesson, Anders
    et al.
    University of Borås, School of Engineering.
    Curtarolo, Stefano
    Harutyunyan, Avetik R.
    Bolton, Kim
    University of Borås, School of Engineering.
    Computational study of the thermal behavior of iron clusters on a porous substrate2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 77, no 11Article in journal (Refereed)
    Abstract [en]

    The thermal behavior of iron nanoclusters on a porous substrate has been studied using classical molecular dynamics simulations. The substrate has been modeled with a simple Morse potential and pores with different shapes have been modeled in order to mimic the porous substrates used for carbon nanotube growth. It has been confirmed that the presence of the substrate increases the cluster melting temperature compared to the free cluster. In addition, the magnitude of this increase in melting point depends on the existence, shape, and diameter of the pore. For example, the increase in melting point is larger for clusters supported on flat (nonporous) substrates than for clusters which straddle pores with smaller diameters than the cluster diameter.

  • 36.
    Börjesson, Anders
    et al.
    University of Borås, School of Engineering.
    Erdtman, Edvin
    University of Borås, School of Engineering.
    Ahlström, Peter
    University of Borås, School of Engineering.
    Berlin, Mikael
    Andersson, Thorbjörn
    Bolton, Kim
    University of Borås, School of Engineering.
    Molecular modelling of oxygen and water permeation in polyethylene2013In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 54, no 12, p. 2988-Article in journal (Refereed)
    Abstract [en]

    Monte Carlo and molecular dynamics simulations were performed to calculate solubility, S, and diffusion, D, coefficients of oxygen and water in polyethylene, and to obtain a molecular-level understanding of the diffusion mechanism. The permeation coefficient, P, was calculated from the product of S and D. The AMBER force field, which yields the correct polymer densities under the conditions studied, was used for the simulations, and it was observed that the results were not sensitive to the inclusion of atomic charges in the force field. The simulated S for oxygen and water are higher and lower than experimental data, respectively. The calculated diffusion coefficients are in good agreement with experimental data. Possible reasons for the discrepancy in the simulated and experimental solubilities, which results in discrepancies in the permeation coefficients, are discussed. The diffusion of both penetrants occurs mainly by large amplitude, infrequent jumps of the molecules through the polymer matrix.

  • 37.
    Börjesson, Anders
    et al.
    University of Borås, School of Engineering.
    Harutyunyan, Avetik R.
    Curtarolo, Stefano
    Bolton, Kim
    University of Borås, School of Engineering.
    Computational study of the thermal behavior of iron clusters on a porous substrate2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 77, no 11Article in journal (Refereed)
  • 38.
    Börjesson, Anders
    et al.
    University of Borås, School of Engineering.
    Zhu, Wuming
    Amara, Hakim
    Bichara, Christophe
    Bolton, Kim
    University of Borås, School of Engineering.
    Computational studies of metal-carbon nanotube interfaces for regrowth and electronic transport2009In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 9, no 3, p. 1117-1120Article in journal (Refereed)
    Abstract [en]

    First principles and tight binding Monte Carlo simulations show that junctions between single-walled carbon nanotubes (SWNTs) and nickel clusters are on the cluster surface, and not at subsurface sites, irrespective of the nanotube chirality, temperature, and whether the docking is gentle or forced. Gentle docking helps to preserve the pristine structure of the SWNT at the metal interface, whereas forced docking may partially dissolve the SWNT in the cluster. This is important for SWNT-based electronics and SWNT-seeded regrowth.

  • 39. Chelakara Satyanarayana, Kavitha
    et al.
    Bohlén, Martin
    University of Borås, School of Engineering.
    Lund, Anja
    Rychwalski, Rodney
    Bolton, Kim
    University of Borås, School of Engineering.
    Analysis of the torsion angle distribution of poly(vinylidene fluoride) in the melt2012In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 53, no 4, p. 1109-1114Article in journal (Refereed)
    Abstract [en]

    Analysis of the torsionangledistribution of poly(vinylidene fluoride) (PVDF) structures at temperatures above its melting point is addressed by combining first principles methods, atomistic simulations and laboratory experiments. Amorphous, α- and β-conformations of PVDF structures have been considered. The results from the atomistic simulations as well as the experiments show that there is a larger probability of the PVDF torsions to be near ±180° at temperatures above the melting point, which is associated more with the β-conformation than the α-conformation.

  • 40. Chelakara Satyanarayana, Kavitha
    et al.
    Bolton, Kim
    University of Borås, School of Engineering.
    Molecular dynamics simulations of α- to β-poly (vinylidene fluoride) phase change by stretching and poling2012In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 53, no 14, p. 2927-2934Article in journal (Refereed)
    Abstract [en]

    The mechanism of inducing a phase change from α-poly(vinylidene fluoride) (α-PVDF) to β-PVDF is addressed using molecular dynamics simulations based on a molecular mechanics force field. The effect of applying a strain to the α-PVDF crystal along the axis of the molecules is investigated, as well as poling the crystal before or after stretching. Rather large (at least 1010 V/m) electric fields that are perpendicular to the axis of the PVDF molecules are required to induce α- to β-PVDF phase change when no strain is applied to the α-PVDF crystal. However, at a strain of 1.0475 (i.e., when the crystal is stretched by 4.75%) α-PVDF changes to a β-PVDF like structure, where the β-PVDF molecules orientate anti-parallel relative to each other. Transformation of the anti-parallel β-PVDF to β-PVDF can be induced by poling (even at the lowest electric field of 105 V/m studied here) or by thermal annealing.

  • 41. Curtarolo, S.
    et al.
    Awasthi, N.
    Setyawan, W.
    Jiang, A.
    Bolton, Kim
    University of Borås, School of Engineering.
    Tokune, T.
    Harutyunyan, A. R.
    Influence of Mo on the Fe:Mo:C nanocatalyst thermodynamics for singlewalled carbon nanotube growth2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 78, no 5Article in journal (Refereed)
  • 42. Curtarolo, Stefano
    et al.
    Awasthi, Neha
    Setyawan, Wahyu
    Mora, Elena
    Tokune, Toshio
    Bolton, Kim
    University of Borås, School of Engineering.
    Harutyunyan, Avetik R.
    The role of carbon solubility in Fe-C nano-clusters on the growth of small single-walled carbon nanotubes2008Conference paper (Other academic)
  • 43. Curtarolo, Stefano
    et al.
    Awasthi, Neha
    Setyawan, Wahyu
    Tokune, Toshio
    Mora, Elena
    Kuznetsov, O.
    Harutyunyan, Avetik R.
    Bolton, Kim
    University of Borås, School of Engineering.
    The apparent paradox of the Gibbs-Thompson phenomenon is the thermodynamic limit for the activity of Fe anf Fe:Mo catalysts for carbon nanotubes growth2008Conference paper (Other academic)
  • 44. Cutrarolo, Stefano
    et al.
    Awastahi, Neha
    Setyawan, Wahyu
    Li, Na
    Jiang, Aiqin
    Mora, Elena
    Bolton, Kim
    University of Borås, School of Engineering.
    Harutyunyan, Avetik R.
    Thermodynamics of carbon in iron nanoparticles at low temperature: reduced solubility and size-induced nucleation of cementite2010In: Physics Procedia, ISSN 1875-3892, E-ISSN 1875-3892, Vol. 6, p. 16-26Article in journal (Refereed)
    Abstract [en]

    In this manuscript we present the thermodynamics of iron-carbon nano particles at low temperature. By combining classical molecular dynamics simulations, ab initio calculations, finite temperature thermodynamics modeling, and the “size/pressure approximation”, we address carbon-induced fluidization, size-induced eutectic point shift, and reduced solubility at the nanoscale. The results are used to describe, as functions of particle size, three scenarios in the catalytic chemical vapor deposition growth of single single-walled carbon nanotubes, corresponding to steady state-, limitedand no-growth.

  • 45. Ding, Feng
    et al.
    Larsson, Peter
    Larsson, Andreas J.
    Ahuja, Rajeev
    Duan, Haiming
    Rosén, Arne
    Bolton, Kim
    University of Borås, School of Engineering.
    The importance of strong carbon-metal adhesion for catalytic nucleation of single-walled carbon nanotubes2008In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 8, no 2, p. 463-468Article in journal (Refereed)
    Abstract [en]

    Density functional theory is used to show that the adhesion between single-walled carbon nanotubes (SWNTs) and the catalyst particles from which they grow needs to be strong to support nanotube growth. It is found that Fe, Co, and Ni, commonly used to catalyze SWNT growth, have larger adhesion strengths to SWNTs than Cu, Pd, and Au and are therefore likely to be more efficient for supporting growth. The calculations also show that to maintain an open end of the SWNT it is necessary that the SWNT adhesion strength to the metal particle is comparable to the cap formation energy of the SWNT end. This implies that the difference between continued and discontinued SWNT growth to a large extent depends on the carbon-metal binding strength, which we demonstrate by molecular dynamics (MD) simulations. The results highlight that first principles computations are vital for the understanding of the binding strength's role in the SWNT growth mechanism and are needed to get accurate force field parameters for MD.

  • 46. Duan, Haiming
    et al.
    Ding, Feng
    Rosén, Arne
    Harutyunyang, Avetik R.
    Curtarolo, Stefano
    Bolton, Kim
    University of Borås, School of Engineering.
    Size dependent melting mechanisms of iron nanoclusters2007In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 333, no 1, p. 57-62Article in journal (Refereed)
    Abstract [en]

    Molecular dynamics simulations were used to study the change in the mechanism of iron cluster melting with increasing cluster size. Melting of smaller clusters (e.g., Fe-55 and Fe-100) occurs over a large temperature interval where the phase of the cluster repeatedly oscillates between liquid and solid. In contrast, larger clusters (e.g., Fe-300) have sharper melting points with surface melting preceding bulk melting. The importance of the simulation time, the force field and the definition of cluster melting is also discussed.

  • 47. Duan, Haiming
    et al.
    Ding, Feng
    Rosén, Arne
    Harutyunyang, Avetik
    Tokune, Toshio
    Curtarolo, Stefano
    Bolton, Kim
    University of Borås, School of Engineering.
    Initial growth of single-walled carbon nanotubes on supported iron clusters: a molecular dynamics study2007In: European Physical Journal D: Atomic, Molecular and Optical Physics, ISSN 1434-6060, E-ISSN 1434-6079, Vol. 43, no 1-3, p. 185-189Article in journal (Refereed)
    Abstract [en]

    Molecular dynamics simulations were used to study the initial growth of single-walled carbon nanotubes (SWNTs) on a supported iron cluster (Fe-50). Statistical analysis shows that the growth direction of SWNTs becomes more perpendicular to the substrate over time due to the weak interaction between carbon nanotube and the substrate. The diameter of the nanotube also increases with the simulation time and approaches the size of the supported iron cluster.

  • 48. Duan, Haiming
    et al.
    Rosén, Arne
    Harutyunyan, Avetik
    Curtarolo, Stefano
    Bolton, Kim
    University of Borås, School of Engineering.
    Computational studies of small carbon and iron-carbon systems relevant to carbon nanotube growth2008In: Journal of Nanoscience and Nanotechnology, ISSN 1533-4880, E-ISSN 1533-4899, Vol. 8, no 11, p. 6170-6177Article in journal (Refereed)
    Abstract [en]

    Density functional theory (DFT) calculations show that dimers and longer carbon strings are more stable than individual atoms on Fe(111) surfaces. It is therefore necessary to consider the formation of these species on the metal surfaces and their effect on the mechanism of single-walled nanotube (SWNT) growth. The good agreement between the trends (energies and structures) obtained using DFT and those based on the Brenner and AIREBO models indicate that these analytic models provide adequate descriptions of the supported carbon systems needed for valid molecular dynamics simulations of SWNT growth. In contrast, the AIREBO model provides a better description of the relative energies for isolated carbon species, and this model is preferred over the Brenner potential when simulating SWNT growth in the absence of metal particles. However, the PM3 semiempirical model appears to provide an even better description for these systems and, given sufficient computer resources, direct dynamics methods based on this model may be preferred.

  • 49. Erdtman, Edvin
    et al.
    Ahlström, Peter
    University of Borås, School of Engineering.
    Berlin, Mikael
    Andersson, Thorbjörn
    Gkourmpis, Thomas
    Bolton, Kim
    University of Borås, School of Engineering.
    Penetration and absorption of small molecules in polymers2014Conference paper (Refereed)
  • 50.
    Erdtman, Edvin
    et al.
    Linköping Universitet.
    Bohlén, Martin
    University of Borås, Faculty of Textiles, Engineering and Business.
    Ahlström, Peter
    University of Borås, Faculty of Textiles, Engineering and Business.
    Gkourmpis, Thomas
    Borealis AB.
    Berlin, Mikael
    Tetra Pak Packaging Solutions AB.
    Andersson, Thorbjörn
    Tetra Pak Packaging Solutions AB.
    Bolton, Kim
    University of Borås, Faculty of Textiles, Engineering and Business.
    A molecular-level computational study of the diffusion and solubility of water and oxygen in carbonaceous polyethylene nanocomposites2016In: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488, Vol. 54, p. 589-602Article in journal (Refereed)
    Abstract [en]

    Monte Carlo and molecular dynamics simulations were performed to investigate the effect on the solubility, diffusion, and permeability of water and oxygen when adding graphene or single-walled carbon nanotubes (SWCNTs) to polyethylene (PE). When compared with pure PE, addition of graphene lowered the solubility of water, whereas at lower temperatures, the oxygen solubility increased because of the oxygen–graphene interaction. Addition of SWCNTs lowered the solubility of both water and oxygen when compared with pure PE. A detailed analysis showed that an ordered structure of PE is induced near the additive surface, which leads to a decrease in the diffusion coefficient of both penetrants in this region. The addition of graphene does not change the permeation coefficient of oxygen (in the direction parallel to the filler) and, in fact, may even increase this coefficient when compared with pure PE. In contrast, the water permeability is decreased when graphene is added to PE. The addition of SWCNTs decreases the permeability of both penetrants. Graphene can consequently be added to selectively increase the solubility and permeation of oxygen over water, at least at lower temperatures. 

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