Double-hybrid density-functional theory applied to molecular crystals

TL;DR

This study evaluates various double-hybrid density-functional approximations combined with LMP2 for calculating lattice energies of molecular crystals, finding that some methods achieve accuracy comparable to LMP2 but generally do not outperform it.

Contribution

The paper systematically compares double-hybrid density functionals with LMP2 for molecular crystal lattice energies, highlighting the accuracy of PBEsol-based double-hybrids.

Findings

Double-hybrid methods outperform Kohn-Sham calculations.

PBEsol-based double-hybrids achieve ~6 kJ/mol accuracy.

Results verified on dimers and HCN crystal.

Abstract

We test the performance of a number of two- and one-parameter double-hybrid approximations, combining semilocal exchange-correlation density functionals with periodic local second-order M{\o}ller-Plesset (LMP2) perturbation theory, for calculating lattice energies of a set of molecular crystals: urea, formamide, ammonia, and carbon dioxide. All double-hybrid methods perform better on average than the corresponding Kohn-Sham calculations with the same functionals, but generally not better than standard LMP2. The one-parameter double-hybrid approximations based on the PBEsol density functional gives lattice energies per molecule with an accuracy of about 6 kJ/mol, which is similar to the accuracy of LMP2. This conclusion is further verified on molecular dimers and on the hydrogen cyanide crystal.