Integral-direct Hartree-Fock and M{\o}ller-Plesset Perturbation Theory for Periodic Systems with Density Fitting: Application to the Benzene Crystal

TL;DR

This paper introduces an efficient algorithm for periodic Hartree-Fock and MP2 calculations using density fitting, enabling the study of larger systems and providing more accurate cohesive energy predictions for benzene crystals.

Contribution

The authors develop an integral-direct, density-fitted implementation of periodic HF and MP2 that reduces storage needs and allows larger system studies, improving accuracy over previous methods.

Findings

Predicted MP2 cohesive energy of benzene crystal is -72.8 kJ/mol.

New method enables studying systems an order of magnitude larger.

Modified MP2 models approach chemical accuracy for benzene crystal.

Abstract

We present an algorithm and implementation of integral-direct, density-fitted Hartree-Fock (HF) and second-order M{\o}ller-Plesset perturbation theory (MP2) for periodic systems. The new code eliminates the formerly prohibitive storage requirements and allows us to study systems one order of magnitude larger than before at the periodic MP2 level. We demonstrate the significance of the development by studying the benzene crystal in both the thermodynamic limit and the complete basis set limit, for which we predict an MP2 cohesive energy of $-72.8$ kJ/mol, which is about $10$--$15$ kJ/mol larger in magnitude than all previously reported MP2 calculations. Compared to the best theoretical estimate from literature, several modified MP2 models approach chemical accuracy in the predicted cohesive energy of the benzene crystal and hence may be promising cost-effective choices for future applications on molecular crystals.