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  • 1
    Electronic Resource
    Electronic Resource
    Influence of hydrophobic solutes on the dynamic behavior of water (1980)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 84 (1980), S. 2381-2390 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100456a009
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular dynamics simulation of the transport of small molecules across a polymer membrane (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 4699-4704 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The transport of small molecules through a polymer membrane is modeled using the computer simulation technique of molecular dynamics (MD). The transport coefficient is derived from a combination of the excess free energy and the diffusion constant. Both properties are derived from MD simulations, applied to helium and methane in polydimethylsiloxane (PDMS). The diffusional process appears to have the character of a jump diffusion for methane and less so for helium. Jumps are allowed by fluctuations of the size and shape of holes. Experimental diffusion constants are well reproduced. The excess free energies, determined by a particle insertion method, are lower by 5–7 kJ/mol than experimental values. It is shown that, as a result of a higher solubility, methane has a higher permeability constant than helium, despite its lower diffusion constant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462806
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  • 3
    Electronic Resource
    Electronic Resource
    Free energy of ionic hydration: Analysis of a thermodynamic integration technique to evaluate free energy differences by molecular dynamics simulations (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 5876-5886 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The thermodynamic integration technique to evaluate free energy differences by molecular dynamics simulations is analyzed. The hydration of the ions Na+ , K+ , Ca++ , F−, Cl−, and Br− is used as the process to illustrate the potential utility of the method. A neon–water system is used as a reference system. The parameters that influence the performance and accuracy of the thermodynamic integration, in which the potential interaction parameters are gradually and continuously changed, are studied. These parameters include the total simulation time, the magnitude of the time step for the numerical integration of the equations of motion, the system size, and the cutoff radii for the intermolecular interactions. Fast convergence is found for the Gibbs free energy difference between Ne and Na+ with respect to total simulation time. The time step and system size are relatively unimportant. The use of cutoff radii, for the ion–water but especially unfortunately also the water–water intermolecular interactions, seriously influences the results obtained. A simple correction for the use of cutoff radii cannot be made. Results are compared to experimental values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455539
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  • 4
    Electronic Resource
    Electronic Resource
    Molecular dynamics simulation of a smectic liquid crystal with atomic detail (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 3718-3732 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A molecular dynamics simulation of a sodium–decanoate/decanol/water system is reported. The system is treated in full atomic detail, with the exception of CH2 and CH3 groups that are considered to be "united atoms,'' and is a refinement of a previous model membrane [Mol. Phys. 11, 1 (1983)]. The long-range Coulomb interactions were included specifically. The order parameters of the chain units of the lipids and diffusion constants of components in the system calculated from the simulation agree well with those reported in experiments on this model membrane. The overall structure of the membrane shows considerable disorder, with a broad lipid–water interface, extending over approximately 1 nm. The distribution of the components is such that an almost complete charge cancellation occurs throughout the system, which is in contradiction with the generally assumed electrical double layer structure for membranes. A counterion condensation of 70% is observed. Both the translational and the rotational motions of water are slowed down compared to bulk water. The penetration of water into the hydrocarbon region of the membrane is substantial. Pair correlations of various atom pairs, and dihedral statistics and transition rates of the dihedrals in the lipids are reported. The distributions of chain segments of the lipids, of water molecules, and of sodium ions are compared with theoretical predictions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454893
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  • 5
    Electronic Resource
    Electronic Resource
    The quasi-Gaussian entropy theory: Free energy calculations based on the potential energy distribution function (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 1560-1574 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new theory is presented for calculating the Helmholtz free energy based on the potential energy distribution function. The usual expressions of free energy, internal energy and entropy involving the partition function are rephrased in terms of the potential energy distribution function, which must be a near Gaussian one, according to the central limit theorem. We obtained expressions for the free energy and entropy with respect to the ideal gas, in terms of the potential energy moments. These can be linked to the average potential energy and its derivatives in temperature. Using thermodynamical relationships we also produce a general differential equation for the free energy as a function of temperature at fixed volume. In this paper we investigate possible exact and approximated solutions. The method was tested on a theoretical model for a solid (classical harmonic solid) and some experimental liquids. The harmonic solid has an energy distribution, which can be derived exactly from the theory. Experimental free energies of water and methanol could be reproduced very well over a temperature range of more than 300 K. For water, where the appropriate experimental data were available, also the energy and heat capacity could be reproduced very well. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470744
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  • 6
    Electronic Resource
    Electronic Resource
    HYDRATION STRUCTURE OF FIBROUS MACROMOLECULES (1965)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 125 (1965), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1965.tb45403.x
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  • 7
    Electronic Resource
    Electronic Resource
    Free volume properties of a simulated lipid membrane (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 9090-9099 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper, an extensive analysis of free volume related properties of a lipid membrane is given. Using percolation theory, and comparing the free volume properties to those of a soft polymer, additional insights are obtained. The analyses are discussed within the framework of the four region model. It is concluded that the four regions have very different free volume properties. The region containing the dense part of the lipid tails resembles a soft polymer membrane to a large extent. The middle part of the membrane is more similar to a low density alkane. The consequences of the computed free volume properties on the permeation process of small penetrants are discussed. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471442
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  • 8
    Electronic Resource
    Electronic Resource
    Application of the quasi-Gaussian entropy theory to the calculation of thermodynamic properties of water and methane in the liquid and gas phase (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 6665-6678 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this article we investigate the applicability of the statistical Gamma state as following from the quasi-Gaussian entropy theory, where all thermodynamic properties at every temperature are obtained from the knowledge of the potential energy distribution at one temperature. We compared for a typically polar system (water) and an apolar one (methane) the experimental heat capacity and entropy data with the predictions of the theory at various densities, ranging from the almost ideal gas to typical liquids. Interestingly, the behavior of water and methane is quite similar. Low-density gases and fluid-liquid systems can be described as weakly perturbed Gamma states. For intermediate densities a more complex statistical state arises. In order to describe more accurately the fluid-liquid regime, we propose in this paper a confined Gamma state, based on the division of phase-space into two different regions: one of them described by an exact Gamma state and another very unstable one. We conclude that typical fluid-liquids can be described very well by this new Gamma state approximation. We also try to give a physical interpretation of the two parts of phase space that arise from the model. The high accuracy of the theory over a large temperature range makes the approach very suitable for the prediction of thermodynamical properties at, for example, supercritical conditions. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.471385
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  • 9
    Electronic Resource
    Electronic Resource
    The missing term in effective pair potentials (1987)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 91 (1987), S. 6269-6271 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100308a038
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  • 10
    Electronic Resource
    Electronic Resource
    Prediction of the liquid–vapor equilibrium pressure using the quasi-Gaussian entropy theory (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 7022-7025 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We derived a method to evaluate the liquid–vapor equilibrium pressure, with high accuracy over a large range of temperature, using the quasi-Gaussian entropy theory. The final expression that we obtain for the equilibrium pressure as a function of the temperature can be considered as a very accurate approximate solution of the Clausius–Clapeyron equation. The method was applied to water, methanol and mercury, and was compared to two usual approximations of the Clausius–Clapeyron equation. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472503
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