Time-dependent N-electron valence perturbation theory with matrix product state reference wavefunctions for large active spaces and basis sets: Applications to the chromium dimer and all-trans polyenes

Alexander Yu Sokolov; Sheng Guo; Enrico Ronca; Garnet Kin-Lic Chan

doi:10.1063/1.4986975

Time-dependent N-electron valence perturbation theory with matrix product state reference wavefunctions for large active spaces and basis sets: Applications to the chromium dimer and all-trans polyenes

J Chem Phys. 2017 Jun 28;146(24):244102. doi: 10.1063/1.4986975.

Authors

Alexander Yu Sokolov¹, Sheng Guo¹, Enrico Ronca¹, Garnet Kin-Lic Chan¹

Affiliation

¹ Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.

PMID: 28668022
DOI: 10.1063/1.4986975

Abstract

In earlier work [A. Y. Sokolov and G. K.-L. Chan, J. Chem. Phys. 144, 064102 (2016)], we introduced a time-dependent formulation of the second-order N-electron valence perturbation theory (t-NEVPT2) which (i) had a lower computational scaling than the usual internally contracted perturbation formulation and (ii) yielded the fully uncontracted NEVPT2 energy. Here, we present a combination of t-NEVPT2 with a matrix product state (MPS) reference wavefunction (t-MPS-NEVPT2) that allows us to compute uncontracted dynamic correlation energies for large active spaces and basis sets, using the time-dependent density matrix renormalization group algorithm. In addition, we report a low-scaling MPS-based implementation of strongly contracted NEVPT2 (sc-MPS-NEVPT2) that avoids computation of the four-particle reduced density matrix. We use these new methods to compute the dissociation energy of the chromium dimer and to study the low-lying excited states in all-trans polyenes (C₄H₆ to C₂₄H₂₆), incorporating dynamic correlation for reference wavefunctions with up to 24 active electrons and orbitals.