@article{silbermann_klapp_schoen_chennamsetty_bock_gubbins_2006, title={Mesoscale modeling of complex binary fluid mixtures: Towards an atomistic foundation of effective potentials}, volume={124}, ISSN={["1089-7690"]}, DOI={10.1063/1.2161207}, abstractNote={This paper is devoted to equilibrium molecular-dynamics (MD) simulations of a fully atomistic model of binary mixtures of water (component 1) and ethanol (component 2). We investigate ways to extract from these simulations effective, pairwise additive potentials suitable to describe the interactions between coarse-grained molecules (i.e., beads) in corresponding mesoscale dissipative particle-dynamics simulations. The fully atomistic model employed in MD simulations is mapped onto an implicit water model, where the internal degrees of freedom of ethanol and all the degrees of freedom of water are integrated out. This gives us an effective one-component system consisting only of ethanol beads. The effective interaction potential between a pair of ethanol beads, Φ(R), is approximated at three levels of sophistication. At the lowest one, we approximate Φ(R) by the potential of mean force between the centers of mass of two ethanol beads calculated in the fully atomistic MD simulations; at the second level, we take Φ(R) to be the potential linked to total and direct correlation functions in the hypernetted-chain closure of the Ornstein-Zernike equation. At the third level we approximate Φ(R) numerically by improving it iteratively through the Boltzmann inversion scheme. Our results indicate that the level-one approach works only at the lowest (8 wt %) concentration; the level-two approach works only up to intermediate ethanol concentrations (ca. 50 wt %). Only the Boltzmann inversion scheme works for all, up to the highest concentration considered (70 wt %).}, number={7}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Silbermann, JR and Klapp, SHL and Schoen, M and Chennamsetty, N and Bock, H and Gubbins, KE}, year={2006}, month={Feb} }
@article{chennamsetty_bock_gubbins_2005, title={Coarse-grained potentials from Widom's particle insertion method}, volume={103}, ISSN={["1362-3028"]}, DOI={10.1080/00268970500208658}, abstractNote={Widom's particle insertion method is used to calculate effective pair potentials for binary A/B mixtures, where B molecules represent a solvent whose degrees of freedom are integrated out. Comparison of Widom's method with an alternative route via the potential of mean force shows good agreement; however, Widom's particle insertion method experiences sampling difficulties at high densities. An isotherm for a binary mixture of argon (‘solvent’, B) and krypton (‘solute’, A) is calculated. While the structure at the pair level is well represented by the effective system using only effective pair potentials and ignoring all higher multi-body contributions, increasing deviations in the pressure are observed as the density of the effective system is increased. These latter deviations are attributed to the neglect of three- and higher multi-body interactions.}, number={21-23}, journal={MOLECULAR PHYSICS}, author={Chennamsetty, N and Bock, H and Gubbins, KE}, year={2005}, pages={3185–3193} }
@article{chennamsetty_bock_scanu_siperstein_gubbins_2005, title={Cosurfactant and cosolvent effects on surfactant self-assembly in supercritical carbon dioxide}, volume={122}, ISSN={["1089-7690"]}, DOI={10.1063/1.1855291}, abstractNote={The impact of alcohol additives on the self-assembly of surfactants in supercritical carbon dioxide is investigated using lattice Monte Carlo simulations. We observe that all studied (model) alcohols reduce the critical micelle concentration. The reduction is stronger the longer the hydrocarbon chain of the alcohol, and the higher the alcohol concentration. Short-chain alcohols are found to concentrate in the surfactant layer of the aggregates, replacing surfactant molecules and leading to a strong decrease of the aggregation number and a large increase of the number of aggregates. On the other hand, only a small number of alcohol molecules with longer chain length are found in the aggregates, leading to a slight increase in the aggregation number. However, structural properties such as size and density profiles of aggregates at the same aggregation number are not influenced markedly. Consequently, short-chain alcohols act as cosurfactants, directly influencing the properties of the aggregates, while alcohols with longer hydrocarbon chains work as cosolvents, altering the properties of the solvent. However, the transition between both extremes is gradual.}, number={9}, journal={JOURNAL OF CHEMICAL PHYSICS}, author={Chennamsetty, N and Bock, H and Scanu, LF and Siperstein, FR and Gubbins, KE}, year={2005}, month={Mar} }