Beyond the Random-Phase Approximation for the Electron Correlation Energy: The Importance of Single Excitations

Xinguo Ren,Patrick Rinke,Alexandre Tkatchenko,Matthias Scheffler

doi:10.1103/physrevlett.106.153003

Xinguo Ren, Patrick Rinke + Show 2 more

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https://doi.org/10.1103/physrevlett.106.153003

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Abstract

The random-phase approximation (RPA) for the electron correlation energy, combined with the exact-exchange (EX) energy, represents the state-of-the-art exchange-correlation functional within density-functional theory. However, the standard RPA practice--evaluating both the EX and the RPA correlation energies using Kohn-Sham (KS) orbitals from local or semilocal exchange-correlation functionals--leads to a systematic underbinding of molecules and solids. Here we demonstrate that this behavior can be corrected by adding a "single excitation" contribution, so far not included in the standard RPA scheme. A similar improvement can also be achieved by replacing the non-self-consistent EX total energy by the corresponding self-consistent Hartree-Fock total energy, while retaining the RPA correlation energy evaluated using KS orbitals. Both schemes achieve chemical accuracy for a standard benchmark set of noncovalent intermolecular interactions.

Highlights

The random-phase approximation (RPA) for the electron correlation energy, combined with the exactexchange (EX) energy, represents the state-of-the-art exchange-correlation functional within density-functional theory
The standard RPA practice—evaluating both the EX and the RPA correlation energies using Kohn-Sham (KS) orbitals from local or semilocal exchange-correlation functionals—leads to a systematic underbinding of molecules and solids. We demonstrate that this behavior can be corrected by adding a ‘‘single excitation’’ contribution, so far not included in the standard RPA scheme
A similar improvement can be achieved by replacing the non-self-consistent EX total energy by the corresponding self-consistent Hartree-Fock total energy, while retaining the RPA correlation energy evaluated using KS orbitals

Summary

Introduction

The random-phase approximation (RPA) for the electron correlation energy, combined with the exactexchange (EX) energy, represents the state-of-the-art exchange-correlation functional within density-functional theory. EEX@HF is the self-consistent Hartree-Fock energy, whereas the conventional RPA scheme based on PBE orbitals is referred to as ðEXþcRPAÞ@PBE.

Results

Conclusion