Improving the density functional theory description of water with self-consistent polarization

Area of Science:

• Computational Chemistry
• Materials Science
• Physical Chemistry

Background:

• Standard Density Functional Theory (DFT) often neglects crucial dispersion interactions in molecular systems.
• Accurate modeling of hydrogen-bonded systems like water is essential for understanding various chemical and physical processes.
• Existing DFT functionals, such as BLYP and BLYP-D, show limitations in precisely predicting interaction energies and binding characteristics of water clusters.

Purpose of the Study:

• To evaluate the performance of Self-Consistent Polarization Density Functional Theory (SCP-DFT) for modeling water.
• To assess SCP-DFT's ability to accurately capture interaction energies and harmonic frequencies of water clusters.
• To investigate SCP-DFT's predictive power for the properties of liquid water, including radial distribution functions and enthalpy of vaporization.

Main Methods:

• Application of the Self-Consistent Polarization Density Functional Theory (SCP-DFT) to water molecules and clusters.
• Comparison of SCP-DFT results with experimental data and with results from standard DFT functionals (BLYP and BLYP-D).
• Analysis of dimer interaction energies to understand the performance of SCP-DFT.

Main Results:

• SCP-DFT demonstrates significantly improved agreement with experimental interaction energies and harmonic frequencies for water clusters compared to BLYP and BLYP-D.
• SCP-DFT shows errors of only a few tenths of a kcal/mol for interaction energies, outperforming BLYP and BLYP-D which exhibit underbinding and overbinding, respectively.
• While both BLYP and SCP-DFT predict similar, overstructured radial distribution functions for liquid water, SCP-DFT provides a more accurate enthalpy of vaporization.

Conclusions:

• SCP-DFT is an efficient and accurate method for describing large hydrogen-bonded systems, requiring minimal parametrization.
• The inclusion of self-consistent polarization and dispersion interactions by SCP-DFT leads to superior performance over standard DFT functionals for water.
• SCP-DFT holds significant promise for modeling complex systems where hydrogen bonding and dispersion forces are critical.