The Quest for Accurate Liquid Water Properties from First Principles

Abstract

Developing accurate ab initio molecular dynamics (AIMD) models that capture both electronic reorganization and nuclear quantum effects associated with hydrogen bonding is key to quantitative understanding of bulk water and its anomalies as well as its role as a universal solvent. For condensed phase simulations, AIMD has typically relied on the generalized gradient approximation (GGA) of density functional theory (DFT) as the underlying model chemistry for the potential energy surface, with nuclear quantum effects (NQEs) sometimes modeled by performing classical molecular dynamics simulations at elevated temperatures. Here we show that the properties of liquid water obtained from the meta-GGA B97M-rV functional, when evaluated using accelerated path integral molecular dynamics simulations, display accuracy comparable to a computationally expensive dispersion-corrected hybrid functional, revPBE0-D3. We show that the meta-GGA DFT functional reproduces bulk water properties including radial distribution functions, self-diffusion coefficients, and infrared spectra with comparable accuracy of a much more expensive hybrid functional. This work demonstrates that the underlying quality of a good DFT functional requires evaluation with quantum nuclei and that high-temperature simulations are a poor proxy for properly treating NQEs.

Quantifying the hydration structure of sodium and potassium ions: taking additional steps on Jacob's Ladder

“…The effects associated with quantum nuclear effects on the oxygen-oxygen RDF for water have been shown to be quite small for high quality interaction potentials. [51][52][53] The slightly over-structured behaviour of SCAN observed here is consistent with the work of Yao and Kanai 38,54 who also simulated at 300 K with CP2K 55 and CPMD 56 demonstrating good agreement between the two basis set approaches, namely gaussian functions and plane-waves. Simulation of 20 ps utilizing SCAN water in a slab configuration at K using the protocol discussed herein is consistent with the density of 1.05 g/cm 3 calculated by Chen et al.…”

Low-order many-body interactions determine the local structure of liquid water

“…3a demonstrates that, when the simulations are carried out in the NVT ensemble with the density xed at the experimental value, all (2B+3B)-XC PEFs accurately reproduce the experimental O-O RDF, with only revPBE-D3 predicting a slightly over structured liquid. As discussed in the ESI, † the RDFs calculated with the (2B+3B)-XC PEFs using revPBE-D3, B97M-rV, and revPBE0-D3 are in agreement with those reported in the literature from ab initio PIMD simulations carried out with the corresponding functionals, 53,54 which provides evidence for the ability of the present (2B+3B)-XC PEFs to faithfully reproduce the corresponding DFT results at a fraction of the cost associated with fully ab initio simulations. In this context, it should also be noted that small noticeable differences are seen in the comparison between the oxygen-oxygen RDF calculated with the (2B+3B)-revPBE-D3 PEF and the corresponding results from ab initio simulations with the bare revPBE-D3 functional.…”

Quantifying the hydration structure of sodium and potassium ions: taking additional steps on Jacob’s Ladder

“…The effects associated with quantum nuclear effects on the oxygen-oxygen RDF for water have been shown to be quite small for high quality interaction potentials. [51][52][53] The slightly over-structured behaviour of SCAN observed here is consistent with the work of Yao and Kanai 38,54 who also simulated at 300 K with CP2K 55 and CPMD 56 demonstrating good agreement between the two basis set approaches, namely gaussian functions and plane-waves. Simulation of 20 ps utilizing SCAN water in a slab configuration at 300 K using the protocol discussed herein is consistent with the density of 1.05 g/cm 3 calculated by Chen et al.…”