Many-body quantum chemistry for the electron gas: Convergent perturbative theories
James J. Shepherd and Andreas Grüneis
Accepted
We investigate the accuracy of a number of wavefunction based methods at the heart of quantum chemistry for metallic systems. Using Hartree--Fock as a reference, perturbative (M\o ller-Plesset, MP) and coupled cluster (CC) theories are used to study the uniform electron gas model. Our findings suggest that non-perturbative coupled cluster theories are acceptable for modelling electronic interactions in metals whilst perturbative coupled cluster theories are not. Using screened interactions, we propose a simple modification to the widely-used coupled-cluster singles and doubles plus perturbative triples method (CCSD(T)) that lifts the divergent behaviour and is shown to give very accurate correlation energies for the homogeneous electron gas.