eQE 2.0: Subsystem DFT Beyond GGA Functionals

TL;DR

eQE 2.0 advances subsystem DFT by integrating nonlocal functionals and deorbitalized meta GGA functionals, significantly improving accuracy for large systems while maintaining computational efficiency.

Contribution

The paper introduces nonlocal nonadditive kinetic energy and exchange-correlation functionals into eQE 2.0, enhancing accuracy beyond GGA functionals in subsystem DFT.

Findings

eQE 2.0 achieves high accuracy on the S22-5 test set.

The implementation retains linear scaling performance.

eQE 2.0 outperforms conventional Kohn-Sham DFT and CCSD(T).

Abstract

By adopting a divide-and-conquer strategy, subsystem-DFT (sDFT) can dramatically reduce the computational cost of large-scale electronic structure calculations. The key ingredients of sDFT are the nonadditive kinetic energy and exchange-correlation functionals which dominate it's accuracy. Even though, semilocal nonadditive functionals find a broad range of applications, their accuracy is somewhat limited especially for those systems where achieving balance between exchange-correlation interactions on one side and nonadditive kinetic energy on the other is crucial. In eQE 2.0, we improve dramatically the accuracy of sDFT simulations by (1) implementing nonlocal nonadditive kinetic energy functionals based on the LMGP family of functionals; (2) adapting Quantum ESPRESSO's implementation of rVV10 and vdW-DF nonlocal exchange-correlation functionals to be employed in sDFT simulations; (3) implementing "deorbitalized" meta GGA functionals (e.g., SCAN-L). We carefully assess the performance of the newly implemented tools on the S22-5 test set. eQE 2.0 delivers excellent interaction energies compared to conventional Kohn-Sham DFT and CCSD(T). The improved performance does not come at a loss of computational efficiency. We show that eQE 2.0 with nonlocal nonadditive functionals retains the same linear scaling behavior achieved in eQE 1.0 with semilocal nonadditive functionals.