"Polarizable SixPoint Water Models from Computational and Empirical Optimization" Philipp Tröster, Konstantin Lorenzen, and Paul Tavan
J. Phys. Chem. B 118, 15891602 (2014).
Abstract: Tröster et al. (J. Phys. Chem B 2013, 117, 94869500) recently suggested a mixed computational and empirical approach to the optimization of polarizable molecular mechanics (PMM) water models. In the empirical part the parameters of Buckingham potentials are optimized by PMM molecular dynamics (MD) simulations. The computational part applies hybrid calculations, which combine the quantum mechanical description of a H_{2}O molecule by density functional theory (DFT) with a PMM model of its liquid phase environment generated by MD. While the static dipole moments and polarizabilities of the PMM water models are fixed at the experimental gas phase values, the DFT/PMM calculations are employed to optimize the remaining electrostatic properties. These properties cover the width of a Gaussian inducible dipole positioned at the oxygen and the locations of massless negative charge points within the molecule (the positive charges are attached to the hydrogens). While the authors originally considered the cases of one and two negative charges rendering the PMM four and
fivepoint models TL4P and TL5P, here we extend the approach to three negative charges thus suggesting the PMM sixpoint model TL6P. As compared to the predecessors and to other PMM models, which also exhibit partial charges at fixed positions, TL6P turned out to predict all studied properties of liquid water at p_{0} = 1 bar and T_{0} = 300 K with a remarkable accuracy. These properties cover, for instance, the diffusion constant, viscosity, isobaric heat capacity, isothermal compressibility, dielectric constant, density, and the isobaric thermal expansion coecient. This success concurrently provides a microscopic physical explanation of corresponding shortcomings of previous models. It uniquely assigns the failures of previous models to substantial inaccuracies in the description of the higher electrostatic multipole moments of liquid phase water molecules. Resulting favorable properties concerning the transferability to other temperatures and conditions like the melting of ice are also discussed.
BMO authors (in alphabetic order): Konstantin Lorenzen Paul Tavan Philipp Troester
Assoziierte Projekte: Polarizable force fields for molecular mechanics from first principles
