title: A projected approximation to strongly contracted N-electron valence perturbation theory for DMRG wavefunctions.
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.
authors.affiliation: Frick Laboratory, Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Roemelt
authors.affiliation: Frick Laboratory, Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Sheng
authors.initials: S
authors.lastname: Guo
authors.affiliation: Frick Laboratory, Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Garnet K-L
authors.initials: GK
authors.lastname: Chan