Multireference methods for molecular and periodic systems
Laura Gagliardi
Department of Chemistry, and Chemical Theory Center,
University of Minnesota, Minneapolis, Minnesota, 55455, USA
gagliard@umn.edu
I will describe our latest progress in combining density matrix renormalization group
(DMRG) with pair-density functional theory (PDFT) as a new way to calculate
correlation energy. We applied this new approach, called DMRG-PDFT,[1] to study
singlet–triplet gaps in polyacenes and polyacetylenes that require active spaces larger
than the feasibility limit of the conventional complete active-space self-consistent
field (CASSCF) method.
I will also report our advancements in using density matrix embedding theory
(DMET) in combination with CASSCF as a solver and its application to realistic
models of strongly-correlated molecules. We have developed a generalization of
DMET to use a multiconfigurational wave function as a bath, by dividing the active
space into unentangled active subspaces each localized to one fragment. We refer to
this kind of wave function as localized active space (LAS). The LAS bath wave
function can be obtained by the DMET algorithm itself in a self-consistent manner,
and we refer to this approach as the localized active space self-consistent field
(LASSCF) method.[2] Our results for test calculations suggest that LASSCF can be
an appropriate starting point for a perturbative treatment.
matrix renormalization group pair-density functional theory (DMRG-PDFT): singlet–
triplet gaps in polyacenes and polyacetylenes, Chem. Sci., DOI:10.1039/C8SC03569E
(2019) [2] M. Hermes and L. Gagliardi, Multiconfigurational self-consistent field theory with
density matrix embedding: the localized active space self-consistent field method,
submitted (2019)