The Experts below are selected from a list of 195 Experts worldwide ranked by ideXlab platform

Athanassios Z Panagiotopoulos - One of the best experts on this subject based on the ideXlab platform.

  • hydrogen bonding polarizable Intermolecular Potential model for water
    Journal of Physical Chemistry B, 2016
    Co-Authors: Hao Jiang, Othonas A Moultos, Ioannis G Economou, Athanassios Z Panagiotopoulos
    Abstract:

    A polarizable Intermolecular Potential model with short-range directional hydrogen-bonding interactions was developed for water. The model has a rigid geometry, with bond lengths and angles set to experimental gas-phase values. Dispersion interactions are represented by the Buckingham Potential assigned to the oxygen atom, whereas electrostatic interactions are modeled by Gaussian charges. Polarization is handled by a Drude oscillator site, using a negative Gaussian charge attached to the oxygen atom by a harmonic spring. An explicit hydrogen-bonding term is included in the model to account for the effects of charge transfer. The model parameters were optimized to density, configurational energy, pair correlation function, and the dielectric constant of water under ambient conditions, as well as the minimum gas-phase dimer energy. Molecular dynamics and Gibbs ensemble Monte Carlo simulations were performed to evaluate the new model with respect to the thermodynamic and transport properties over a wide ran...

  • optimization of Intermolecular Potential parameters for the co2 h2o mixture
    Journal of Physical Chemistry B, 2014
    Co-Authors: Gustavo A Orozco, Ioannis G Economou, Athanassios Z Panagiotopoulos
    Abstract:

    Monte Carlo simulations in the Gibbs ensemble were used to obtain optimized Intermolecular Potential parameters to describe the phase behavior of the mixture CO2/H2O, over a range of temperatures and pressures relevant for carbon capture and sequestration processes. Commonly used fixed-point-charge force fields that include Lennard-Jones 12–6 (LJ) or exponential-6 (Exp-6) terms were used to describe CO2 and H2O Intermolecular interactions. For force fields based on the LJ functional form, changes of the unlike interactions produced higher variations in the H2O-rich phase than in the CO2-rich phase. A major finding of the present study is that for these Potentials, no combination of unlike interaction parameters is able to adequately represent properties of both phases. Changes to the partial charges of H2O were found to produce significant variations in both phases and are able to fit experimental data in both phases, at the cost of inaccuracies for the pure H2O properties. By contrast, for the Exp-6 case...

  • new Intermolecular Potential models for benzene and cyclohexane
    Journal of Chemical Physics, 1999
    Co-Authors: Jeffrey R Errington, Athanassios Z Panagiotopoulos
    Abstract:

    New Intermolecular Potential models for benzene and cyclohexane have been developed, parameterized to the vapor–liquid coexistence properties. The models utilize the Buckingham exponential-6 Potential to describe nonbonded interactions. Histograms reweighting grand canonical Monte Carlo methods were used to obtain the model parameters. A new algorithm for insertion of molecules with complex molecular architectures or stiff intramolecular constraints has been developed. The algorithm is based on the creation of a reservoir of ideal chains from which structures are selected for insertion during a simulation run. The new Potential models reproduce the experimental saturated liquid densities and vapor pressures to within average absolute deviations of 0.3% and 2.2%, respectively. Critical parameters are also in good agreement with experiment. The infinite dilution behavior of these two cyclic molecules in water was studied. A combination of Widom insertion and expanded ensemble techniques were used to determine the Henry’s law constant of benzene and cyclohexane in water. The results obtained have qualitatively correct temperature dependence. However, the Henry’s constant of benzene in water is overestimated and that of cyclohexane is underestimated at all temperatures by approximately a factor of 3.

Jiali Gao - One of the best experts on this subject based on the ideXlab platform.

  • development of a polarizable Intermolecular Potential function pipf for liquid amides and alkanes
    Journal of Chemical Theory and Computation, 2007
    Co-Authors: Wangshen Xie, Alexander D Mackerell, Jiali Gao
    Abstract:

    A polarizable Intermolecular Potential function (PIPF) employing the Thole interacting dipole (TID) polarization model has been developed for liquid alkanes and amides. In connection with the internal bonding terms of the CHARMM22 force field, the present PIPF-CHARMM Potential provides an adequate description of structural and thermodynamic properties for liquid alkanes and for liquid amides through molecular dynamics simulations. The computed heats of vaporization and liquid density are within 1.4% of experimental values. Polarization effects play a major role in liquid amides, which are reflected by an increase of 1.5−1.8 D in molecular dipole moment for primary and secondary amides. Furthermore, the computed polarization energies contribute to the total Intermolecular interaction energy by 6−24%. The ability of the PIPF-CHARMM force field to treat protein backbone structures is tested by examining the Potential energy surface of the amide bond rotation in N-methylacetamide and the Ramachandran surface ...

  • Simulation of Liquid Amides Using a Polarizable Intermolecular Potential Function
    The Journal of Physical Chemistry, 1996
    Co-Authors: Jiali Gao, Joseph J. Pavelites, Dariush Habibollazadeh
    Abstract:

    We have developed a polarizable Intermolecular Potential function (PIPF) for simulation of liquid amides. The PIPF Potential includes a pairwise additive component, consisting of the familiar Lenna...

Dariush Habibollazadeh - One of the best experts on this subject based on the ideXlab platform.

William Y. Svrcek - One of the best experts on this subject based on the ideXlab platform.

  • Viscosity prediction from a modified square well Intermolecular Potential model
    Fluid Phase Equilibria, 1996
    Co-Authors: Wayne D. Monnery, Anil K. Mehrotra, William Y. Svrcek
    Abstract:

    A statistical mechanical based model for simultaneously calculating liquid and gas phase viscosities using the square well Intermolecular Potential has been developed. Theoretical results are utilized along with modifications to correct the model for the molecular chaos assumption and the inadequacy of the square well Potential. The radial distribution function values are determined from perturbation theory. Model parameters are obtained from liquid and gas viscosity data and generalized with group contributions. With the resulting model, liquid and gas viscosities of a variety of nonpolar compounds are correlated within 5% and 3%, respectively, and predicted within 8% and 5%, respectively.

Kazuo Kitaura - One of the best experts on this subject based on the ideXlab platform.

  • A procedure to generate ab initio Intermolecular Potential function
    Fluid Phase Equilibria, 1995
    Co-Authors: Kazuo Kitaura
    Abstract:

    Abstract A procedure is presented for generating an Intermolecular Potential function from the ab initio MO calculations. Our Potential function consists of the electrostatic, polarization, exchange and charge-transfer and dispersion Potentials. According to the procedure, we derived the Intermolecular Potential function for ammonia dimer from the ab initio MO calculations with the DZP basis set at the MP2 level. The Potential function well reproduced the optimized geometry and the binding energy of the dimer obtained from the ab initio calculations. The heat capacity calculated from the Monte Carlo simulation with the Potential function agreed well with the experimental value, while the NN radial distribution function was in roughly accord with the experiment.