A projected approximation to strongly contracted N-electron valence perturbation theory for DMRG wavefunctions

Michael Roemelt; Sheng Guo; Garnet K-L Chan

doi:10.1063/1.4950757

A projected approximation to strongly contracted N-electron valence perturbation theory for DMRG wavefunctions

J Chem Phys. 2016 May 28;144(20):204113. doi: 10.1063/1.4950757.

Authors

Michael Roemelt¹, Sheng Guo¹, Garnet K-L Chan¹

Affiliation

¹ Frick Laboratory, Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.

PMID: 27250285
DOI: 10.1063/1.4950757

Abstract

A novel approach to strongly contracted N-electron valence perturbation theory (SC-NEVPT2) as a means of describing dynamic electron correlation for quantum chemical density matrix renormalization group (DMRG) calculations is presented. In this approach the strongly contracted perturber functions are projected onto a renormalized Hilbert space. Compared to a straightforward implementation of SC-NEVPT2 with DMRG wavefunctions, the computational scaling and storage requirements are reduced. This favorable scaling opens up the possibility of calculations with larger active spaces. A specially designed renormalization scheme ensures that both the electronic ground state and the perturber functions are well represented in the renormalized Hilbert space. Test calculations on the N2 and [Cu2O2(en)2](2+) demonstrate some key properties of the method and indicate its capabilities.