Development of Polarizable Models for Molecular Mechanical Calculations. 3. Polarizable Water Models Conforming to Thole Polarization Screening Schemes

Abstract

As an integrated step towards a coherent polarizable force field for biomolecular modeling, we analyzed four polarizable water models to evaluate their consistencies with the Thole polarization screening schemes utilized in our latest Amber polarizable force field. Specifically, we studied the performance of both the Thole linear and exponential schemes in these water models to assess their abilities to reproduce experimental water properties. The analysis shows that the tested water models reproduce most of the room-temperature properties of liquid water reasonably well, but fall short of reproducing the dynamic properties and temperature-dependent properties. This study demonstrates the necessity to further fine-tune water polarizable potentials for more robust polarizable force fields for biomolecular simulations.

Determining polarizable force fields with electrostatic potentials from quantum mechanical linear response theory

“…The Drude model and induced dipole model are essentially equivalent. 6,19,20 Both use dipole moments to represent polarization effects. The difference is in the models of the dipole: the induced dipole model uses atom-centered point dipole moments, while for the Drude model, the Drude particles attached to the atom sites through a spring are used to represent the polarization effects.…”

“…The atomic polarizabilities are the key parameters in the induced dipole model. In previous studies, the atomic polarizabilities were calculated by fitting to the molecular polarizabilities, 20,[32][33][34][35] which are obtained either from experimental results or from high-quality QM results. Soteras et al calculated the atomic polarizabilities by fitting the induction energy computed in the perturbation theory.…”

Quantum mechanical force field for water with explicit electronic polarization

“…The quality of the XP3P quantum mechanical potential for these two critical thermodynamic properties is comparable to that of the widely used SPC, TIP3P and TIP4P models for water 8,9 and to that of the recent polarizable models. 10,26,78,114 The distribution of the magnitudes of monomer dipole moments from polarized wave functions in the liquid is shown in Figure 3; these dipole moments span a range from 2.1 to 2.9 D, and they yield an average μ liq of 2.524 ± 0.002 D. The width at half maximum in the dipole distribution is 0.30 D (a half-width of 0.8 D was reported for the AMOEBA model, 10 which seems to be unrealistically large). Clearly, there is a major enhancement of the molecular dipole moment in the liquid, amounting to an increase over 35% relative to the gas phase value.…”

“…132 It is known that non-polarizable potentials for water, such as SPC, TIP3P, and TIP4P, tend to overestimate the self-diffusion coefficient, while most polarizable force fields, including the present XP3P model, show significant improvement. 10,26,78,114 The computed diffusion coefficient is also affected by finite size of the simulation box, and extrapolation to infinity will further increase the value of the diffusion coefficient. 133 The rotational correlation times, τ rotation axis.…”

“…136 In comparison with other models, the present XP3P model performs well for these dynamic properties. 10,26,114 The structure of liquid water is characterized by radial distribution functions (RDFs), g xy (r), which gives the probability of finding an atom of type y at a distance r from an atom of type x relative to the bulk. The RDFs computed at 25…”