Simple Liquid Models with Corrected Dielectric Constants

Abstract

Molecular simulations often use explicit-solvent models. Sometimes explicit-solvent models can give inaccurate values for basic liquid properties, such as the density, heat capacity, and permittivity, as well as inaccurate values for molecular transfer free energies. Such errors have motivated the development of more complex solvents, such as polarizable models. We describe an alternative here. We give new fixed-charge models of solvents for molecular simulations – water, carbon tetrachloride, chloroform and dichloromethane. Normally, such solvent models are parameterized to agree with experimental values of the neat liquid density and enthalpy of vaporization. Here, in addition to those properties, our parameters are chosen to give the correct dielectric constant. We find that these new parameterizations also happen to give better values for other properties, such as the self-diffusion coefficient. We believe that parameterizing fixed-charge solvent models to fit experimental dielectric constants may provide better and more efficient ways to treat solvents in computer simulations.

Absolute proton hydration free energy, surface potential of water, and redox potential of the hydrogen electrode from first principles: QM/MM MD free-energy simulations of sodium and potassium hydration

“…However, maintaining the compatibility between QM and MM interaction representations remains a vital constraint. Since most water models (rigid as well as flexible) are compatible with Mulliken charges obtained at the HF, B3LYP, and MP2 levels of theory, 239 the change to more advanced basis set (e.g., cc-pVXZ family 312 ) will simultaneously require the application of more advanced water models (e.g., the H2O-DC model 235 which, due to its increased partial charges, presents a better compatibility with NPA-derived charges 250 ).…”

“…234 The non-bonded (electrostatic and Lennard-Jones) interactions were truncated at cutoff distance R C = 1.8 nm on the basis of distances between individual atoms 220 recalculated at every time step (no pairlist used). A reaction-field correction 211,212 was applied to account for the mean effect of electrostatic interactions beyond the cutoff distance, using a relative dielectric permittivity of 71.1 as appropriate for the SPC/E water model 235 (see also Refs. 236-238).…”

A Fixed-Charge Model for Alcohol Polarization in the Condensed Phase, and Its Role in Small Molecule Hydration

“…This process is a variation of previous work 33 with a focus placed specifically on small molecules containing hydroxyl groups. The simplest of such solutes is methanol, and Figure 1 shows an example optimization flow process for methanol.…”

Predicting water-to-cyclohexane partitioning of the SAMPL5 molecules using dielectric balancing of force fields

“…We have recently been interested in exploring dielectric behavior as a possible route to improving force fields in classical molecular simulations [14, 15]. Modulation of standard force fields to correct for what is often flawed dielectric behavior could have beneficial consequences for molecule transferability in condensed-phase environments.…”

“…Modulation of standard force fields to correct for what is often flawed dielectric behavior could have beneficial consequences for molecule transferability in condensed-phase environments. The static dielectric constant has traditionally not been a core target experimental observable in force field development because of its more prohibitive computational cost, particularly for highly polar molecules where it tends to converge slowly [14]. Methods that have utilized the static dielectric constant in force field optimization have shown improved properties in comparisons with experiment [14, 16], in particular hydration free energies [15].…”