A projected approximation to strongly contracted N-electron valence perturbation theory for DMRG wavefunctions
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 N_2 and [Cu_2O_2(en)_2]^(2+) demonstrate some key properties of the method and indicate its capabilities.
© 2016 AIP Publishing. Received 3 March 2016; accepted 4 May 2016; published online 26 May 2016. This work has been funded by the Otto-Hahn award program of the Max-Planck society as well as the US National Science Foundation through Award No. CHE-1265277. Furthermore, M.R. gratefully acknowledges a Research Fellowship of the "Deutsche Akademischer Austausch-Dienst" (DAAD).
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