Using density functional theory to understand the properties of water
Using density functional theory to understand the properties of water lead image
The structural and dynamic properties of water can be analyzed via computer simulations using quantum mechanical techniques grounded in density functional theory (DFT). Scientists from the Pacific Northwest Laboratory in Washington built upon the understanding of the efficacy of DFT by testing a popular gradient corrected functional protocol, the revised Perdew-Burke-Ernzerhof plus Grimme’s third generation of dispersion (revPBE-D3), to paint a quantifiable, clear, and comprehensive picture of mass density fluctuations in water at both short and long length scales and under isothermal and isobaric conditions. They report their findings in The Journal of Chemical Physics in June 2017.
The researchers compared their revPBE-D3 protocol results against the Becke-Lee-Yang-Parr plus Grimme dispersion corrections (BLYP-D2) protocol and two potentials: the empirical fixed charged model (SPC/E) and the many-body potential model (MB-pol). Their results demonstrate the broad range of local environments in which DFT-based potentials contrast against the SPC/E and MB-pol potentials. A key finding of the research is that the revPBE-D3 offers a reasonable reproduction at 300K of the structure, density of water and of the isothermal compressibility (an important property to understand the behavior of water at low temperatures). Also, all three models are able to produce free energy needed for the formation of a molecular sized cavity and fluctuations that govern surface tension, despite the models’ differed characterizations of local structure and compressibility.
The authors highlight that this research examines the thermodynamic properties of surface tension and isothermal compressibility that builds upon the theory of hydrophobicity and solvation. Author Christopher Mundy adds that although revPBE-D3 water has known deficiencies, its use under suitable protocol provides an accurate and affordable description of water that impacts our understanding of solvation in a variety of chemical environments.
Source: “Mass density fluctuations in quantum and classical descriptions of liquid water,” by Mirza Galib et al., Journal of Chemical Physics (2017). The article can be accessed at https://doi.org/10.1063/1.4986284 .
