Systematic Optimization of Water Models Using Liquid/Vapor Surface Tension Data

Abstract

In this work we investigate whether experimental surface tension measurements, which are less sensitive to quantum and self-polarization corrections, are able to replace the usual reliance on the heat of vaporization as experimental reference data for fitting force field models of molecular liquids. To test this hypothesis we develop the fitting protocol necessary to utilize surface tension measurements in the ForceBalance optimization procedure in order to determine revised parameters for both three-point and four-point water models, TIP3P-ST and TIP4P-ST. We find that the incorporation of surface tension in the fit results in a rigid three-point model that reproduces the correct temperature of maximum density of water for the first time, but also leads to over-structuring of the liquid and less accurate transport properties. The rigid four-point TIP4P-ST model is highly accurate for a broad range of thermodynamic and kinetic properties, with similar performance compared to recently developed fourpoint water models. The results show surface tension to be a useful fitting property in general, especially when self-polarization corrections or nuclear quantum corrections are not readily available for correcting the heat of vaporization as is the case for other molecular liquids.

Development and Validation of AMBER-FB15-Compatible Force Field Parameters for Phosphorylated Amino Acids

“…In the parameterization of AMBER-FB15, the parameters were fit to a large data set consisting of RI-MP2/aug-cc-pVTZ-level , calculations on blocked dipeptide versions of the 20 canonical amino acids in standard and alternate protonation states, including relative potential energies and gradients of constrained optimized structures on dense grids of main-chain and side-chain dihedral angle constraints, and vibrational frequencies at optimized geometries. The parameters were optimized in automated fashion using ForceBalance, a program which has been successfully used for systematic and reproducible force field parameterization for a variety of systems. − Although AMBER-FB15 produced notably improved predictions of equilibrium and temperature-dependent properties of proteins, the original work did not develop compatible parameters for PTMs such as phosphorylation.…”

Systematic optimization of a fragment-based force field against experimental pure-liquid properties considering large compound families: application to oxygen and nitrogen compounds

“…The goal of CombiFF is the automated refinement of force-field parameters against experimental condensed-phase data, considering entire classes of organic molecules constructed using a fragment library via combinatorial isomer enumeration. The main steps of the scheme are: This scheme borrows from earlier work on isomer enumeration [79][80][81][82] and topology construction, [83][84][85][86][87][88][89][90][91][92][93][94][95] as well as on automated single-compound force-field optimization approaches such as the POP scheme, 96,97 the ForceBalance scheme, 46,[98][99][100][101][102][103][104][105] and the related schemes. [106][107][108][109][110][111] One key feature of CombiFF is that once the time-consuming task of target-data selection/curation has been performed, the optimization of a force field is entirely automatic, given access to a sufficient number of processors, and only requires a few days of wall-clock computational time.…”

Nuclear Quantum Effect and Its Temperature Dependence in Liquid Water from Random Phase Approximation via Artificial Neural Network

“…Liquid water has been one of the most widely studied systems, and it is arguably the most important application using the FPMD method. − Yet, an accurate description of liquid water has remained elusive for FPMD simulation. Unlike for classical molecular dynamics simulations in which empirical parameters can be tuned to ensure that the experimental values are obtained for physical properties, − a number of liquid water properties from FPMD simulation can deviate quite substantially from their corresponding experimental values . In recent years, understanding the delicate interplay between the underlying electronic structure theory approximation of FPMD and the classical-particle approximation to nuclei, particularly concerning for protons, has become an important focus in the literature. , This problem is made further complicated by the plaguing difficulty of achieving statistical convergence for calculated properties in practice because of the significant computational cost of FPMD simulation. , …”