Simulations of ice and liquid water over a range of temperatures using the fluctuating charge model

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376

426

The five-site transferable interaction potential ͑TIP5P͒ for water ͓M. W. Mahoney and W. L. Jorgensen, J. Chem. Phys. 112, 8910 ͑2000͔͒ is most accurate at reproducing experimental data when used with a simple spherical cutoff for the long-ranged electrostatic interactions. When used with other methods for treating long-ranged interactions, the model is considerably less accurate. With small modifications, a new TIP5P-like potential can be made which is very accurate for liquid water when used with Ewald sums, a more physical and increasingly more commonly used method for treating long-ranged electrostatic interactions. The new model demonstrates a density maximum near 4°C, like the TIP5P model, and otherwise is similar to the TIP5P model for thermodynamic, dielectric, and dynamical properties of liquid water over a range of temperatures and densities. An analysis of this and other commonly used water models reveals how the quadrupole moment of a model can influence the dielectric response of liquid water.

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A reoptimization of the five-site water potential (TIP5P) for use with Ewald sums

Rick

2004

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376

426

“…43 Three different water potentials are used: SPC/E, 44 TIP4P/Ice, 45 and TIP4P-FQ/Ice. 46 The SPC/E potential is a commonly used potential, which has been applied in many studies of clathrate hydrates. The TIP4P/Ice model is a reparametrization of the TIP4P model, 47 which accurately reproduces the densities and phase coexistence properties of many of the ice phases.…”

Section: Methodsmentioning

confidence: 99%

“…45 The TIP4P-FQ/Ice model is a polarizable model, a reparametrization of the TIP4P-FQ model, 48 which gives an accurate density and melting point for ice Ih. 46 All simulations are done in the isothermal-isobaric ͑con-stant T-P-N͒ ensemble by coupling to a pressure bath and a Nosé-Hoover temperature bath. [50][51][52][53][54] An orthorhombic simulation box is used, with each side of the box treated as an independent variable for the constant pressure dynamics.…”

Section: Methodsmentioning

confidence: 99%

Proton disorder and the dielectric constant of type II clathrate hydrates

Rick

Freeman

2010

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Computational studies are presented examining the degree of proton disorder in argon and molecular hydrogen sII clathrate hydrates. Results are presented using a variety of model potentials for the dielectric constant, the proton order parameter, and the molecular volume for the clathrate systems. The dielectric constant for the clathrate systems is found to be lower than the dielectric constant of ice in all models. The ratio of the clathrate to ice dielectric constant correlates well with the ratio of the densities, which is not the case for comparisons to the liquid, so that differences in the dielectric constants between ice and the clathrates are most likely due to differences in densities. Although the computed dielectric constant is a strong function of the model potential used, the ratio of the dielectric constant of ice to that of the clathrates is insensitive to the model potential. For the nonpolar guest molecules used in the current study, the degree proton of disorder is found to depend weakly on the identity of the guest but the dielectric constant does not appear to be sensitive to pressure or the type of guest.

“…For this reason the formulation of new methodologies aimed at combining the advantages of both ab initio and empirical techniques is a very active area of research. [1][2][3][4][5][6][7][8][9][10][11][12][13] We recently proposed a molecular-dynamics ͑MD͒ implementation of an ab initio parametrized polarizable force field ͑PFF͒. 14 In this method, which may be considered an extension of the chemical-potential equalization scheme, [15][16][17][18] the total density of the system was defined as the sum of a reference 0 and a response density ␦ .…”

Section: Introductionmentioning

confidence: 99%

A density-functional approach to polarizable models: A Kim-Gordon response density interaction potential for molecular simulations

Tabacchi

Hutter

Mundy

2005

A combined linear-response-frozen electron-density model has been implemented in a molecular-dynamics scheme derived from an extended Lagrangian formalism. This approach is based on a partition of the electronic charge distribution into a frozen region described by Kim-Gordon theory ͓J. Chem. Phys. 56, 3122 ͑1972͒; J. Chem. Phys. 60, 1842 ͑1974͔͒ and a response contribution determined by the instantaneous ionic configuration of the system. The method is free from empirical pair potentials and the parametrization protocol involves only calculations on properly chosen subsystems. We apply this method to a series of alkali halides in different physical phases and are able to reproduce experimental structural and thermodynamic properties with an accuracy comparable to Kohn-Sham density-functional calculations.