Tetrahedrality and hydrogen bonds in water.

We carried out extensive calculations of liquid water at different temperatures and pressures using the BK3 model suggested recently [P. T. Kiss and A.

Efficient Handling of Gaussian Charge Distributions: An Application to Polarizable Molecular Models.

We present a mesh-based Ewald summation method that is suitable for the calculation of the electrostatic interaction between Gaussian charge distributions, instead of point charges. As an application, we implemented the method in the Gromacs simulation package and tested it with a polarizable water model, showing that the interaction between Gaussian charge distributions can be computed with a small (10%) additional computational cost with respect to the point charge case. In addition, since the performance of polarizable models is strongly influenced by the number of iterations required for the self-consistent field solution, we tested also the Always Stable Predictor-Corrector (ASPC) method of Kolafa (Kolafa, J.

A new polarizable force field for alkali and halide ions.

We developed transferable potentials for alkali and halide ions which are consistent with our recent model of water [P. T. Kiss and A.

A systematic development of a polarizable potential of water.

Based on extensive studies of existing potentials we propose a new molecular model for water. The new model is rigid and contains three Gaussian charges. Contrary to other models, all charges take part in the polarization of the molecule.

Testing the recent charge-on-spring type polarizable water models. II. Vapor-liquid equilibrium.

We studied the vapor-liquid coexistence region of seven molecular models of water. All models use the charge-on-spring (COS) method to express polarization. The studied models were the COS∕G2, COS∕G3 [H.

Testing recent charge-on-spring type polarizable water models. I. Melting temperature and ice properties.

We determined the freezing point of eight molecular models of water. All models use the charge-on-spring (COS) method to express polarization. The studied models were the COS/G2, COS/G3 [H.

Density maximum and polarizable models of water.

To estimate accurately the density of water over a wide range of temperatures with a density maximum at 4 °C is one of the most stringent tests of molecular models. The shape of the curve influences the ability to describe critical properties and to predict the freezing temperature. While it was demonstrated that with a proper parameter fit nonpolarizable models can approximate this behavior accurately, it is much more difficult to do this for polarizable models.

Surface properties of the polarizable Baranyai-Kiss water model.

The water surface properties using the Baranyai-Kiss (BK) model [A. Baranyai and P. T.

On the pressure calculation for polarizable models in computer simulation.

We present a short overview of pressure calculation in molecular dynamics or Monte Carlo simulations. The emphasis is given to polarizable models in order to resolve the controversy caused by the paper of M. J.

Polarizable model of water with field-dependent polarization.

The polarizable charge-on-spring model of water with three Gaussian charges developed by the present authors [A. Baranyai and P. T.

Transferable model of water with variable molecular size.

By decreasing the steepness of the repulsive wing in the intermolecular potential, one can extend the applicability of a water model to the high pressure region. Exploiting this trivial possibility, we published a polarizable model of water which provided good estimations not only of gas clusters, ambient liquid, hexagonal ice, but ice VII at very high pressures as well [A. Baranyai and P.

Sources of the deficiencies in the popular SPC/E and TIP3P models of water.

Motivated by the results of Vega et al. [J. Phys.

A transferable classical potential for the water molecule.

We developed a new model for the water molecule which contains only three Gaussian charges. Using the gas-phase geometry the dipole moment of the molecule matches, the quadrupole moment closely approximates the experimental values. The negative charge is connected by a harmonic spring to its gas-phase position.

Clusters of classical water models.

The properties of clusters can be used as tests of models constructed for molecular simulation of water. We searched for configurations with minimal energies for a small number of molecules. We identified topologically different structures close to the absolute energy minimum of the system by calculating overlap integrals and enumerating hydrogen bonds.

A computationally less demanding charge-on-spring model for the water molecule.

We developed a new charge-on-spring model for the water molecule with the advantage of being computationally less demanding. We start from the basic geometry of Lamoureux et al. [J.

Classical interaction model for the water molecule.

The authors propose a new classical model for the water molecule. The geometry of the molecule is built on the rigid TIP5P model and has the experimental gas phase dipole moment of water created by four equal point charges. The model preserves its rigidity but the size of the charges increases or decreases following the electric field created by the rest of the molecules.

Molecular dynamics simulation with stochastically constrained pressure.

The authors propose a new algorithm for molecular dynamics simulation. The method includes a Monte Carlo scheme for incrementing the dilation rate in the equations of motion. The new algorithm needs no extra computation and the dynamics of the system preserves its continuity.

Limitations of the rigid planar nonpolarizable models of water.

We analyzed the ability of variants of the SPC/E and TIP4P types of water models to describe the temperature dependence of their second virial coefficients, liquid-vapor phase envelopes, and corresponding coexistence vapor pressure. We complete the characterization of the two most promising models by testing their adequacy to predict the structure of the 13 known crystalline phases of ice by (Parrinello-Rahman) isothermal-isobaric Monte Carlo simulations. While these models perform well for the description of properties to which their force fields were fitted (density, heat of vaporization, structure at the level of pair correlations), their transferability to the entire phase diagram is unsatisfactory, i.

Computer simulation of the 13 crystalline phases of ice.

As a reference for follow-up studies toward more accurate model parametrizations, we performed molecular-dynamics and Monte Carlo simulations for all known crystalline phases of ice, as described by the simple point-charge/extended and TIP4P water models. We started from the measured structures, densities, and temperatures, and carried out classical canonical simulations for all these arrangements. All simulated samples were cooled down close to 0 K to facilitate the comparison with theoretical estimates.

Direct estimation of the partition function from computer simulation.

We propose an approximate method for directly estimating the partition function of classical, many-body model systems. The accessible part of the phase space is determined from a single simulation. We introduce the method for the hard-sphere fluid and solid.