Thursday, January 16, 2014

Bulk Liquid Water at Ambient Temperature and Pressure from MP2 Theory

Mauro Del Ben, Mandes Schönherr, Jürg Hutter, and Joost VandeVondele. J. Phys. Chem. Lett. 2013, 4, 3753−3759. DOI: 10.1021/jz401931f
Contributed by François-Xavier Coudert.

Reprinted with permission from doi:10.1021/jz401931f
Copyright 2013 American Chemical Society.

Let's start with the obvious: molecular simulation of liquid water is a very challenging, yet very important, part of our field. While MP2 (second-order perturbation theory) gives a highly accurate description of water-water interactions in water clusters, it was so far too computationally expensive to perform decent-scale molecular dynamics and Monte Carlo simulations of bulk liquid water.

Well, no more. Using large HPC resources, in particular the European PRACE Research Infrastructure and the Swiss National Supercomputer Centre, Mauro Del Ben et al. report in J. Phys. Chem. Lett. the first “truly first-principles simulation of liquid water in the NpT ensemble”. They performed a isobaric-isothermal Monte Carlo simulation, at the MP2 level, of 64 water molecules in a periodic simulation cell, under ambient conditions. The resulting density and structure of the liquid water are quite good, and are contrasted in particular with the less-than-stellar densities yielded by DFT-based methods.

These results represent the latest step in a series of papers these past few years, harnessing the ever-growing power of HPC capabilities to test the validity of quantum chemical calculations for the description of bulk liquid water. Some of the earlier episodes can be read here: