Double-hybrid density-functional theory applied to molecular crystals

Area of Science:

• Computational chemistry
• Solid-state physics
• Quantum chemistry

Background:

• Accurate calculation of lattice energies is crucial for understanding molecular crystals.
• Double-hybrid approximations offer a promising route to improve upon standard density functional theory and perturbation theory methods.

Purpose of the Study:

• To assess the performance of various double-hybrid approximations for computing lattice energies of molecular crystals.
• To compare the accuracy of these methods against standard local second-order Møller-Plesset (LMP2) perturbation theory and Kohn-Sham calculations.

Main Methods:

• The study employed one- and two-parameter double-hybrid approximations.
• These methods combined semilocal exchange-correlation density functionals with periodic local second-order Møller-Plesset (LMP2) perturbation theory.
• Calculations were performed for urea, formamide, ammonia, and carbon dioxide molecular crystals, as well as molecular dimers and the hydrogen cyanide crystal.

Main Results:

• All tested double-hybrid methods showed improved performance over Kohn-Sham calculations with identical functionals.
• However, their performance was generally not superior to standard LMP2.
• One-parameter double-hybrid approximations utilizing the PBEsol density functional achieved lattice energies with an accuracy of approximately 6 kJ/mol, matching LMP2's accuracy.

Conclusions:

• Double-hybrid approximations, particularly one-parameter variants with PBEsol, provide accurate lattice energies for molecular crystals.
• These methods represent a valuable advancement in computational materials science, offering accuracy comparable to established techniques like LMP2.