In recent years there has been a surge in the development of affordable wave-function based methods that can accurately model the electronic structure of solid-state systems and meaningfully predict their properties. The density matrix embedding theory (DMET) algorithm was recently formulated by our group using a restricted closed-shell Hartree Fock (RHF) bath for periodic systems and was used to study the ground state and band structure of one-dimensional solids. In this work, we introduce a restricted open-shell Hartree Fock (ROHF) bath and multireference impurity solvers, specifically, complete-active space self-consistent field (CASSCF) and n-electron valence state second-order perturbation theory (NEVPT2) within the DMET framework to study electronic excitations in solid-state defects. In particular, we have used it to perform numerical tests on an oxygen vacancy on a MgO(100) surface and a neutral silicon vacancy in diamond. We compare excitation energies by performing DMET using the NEVPT2 solver, denoted as NEVPT2-DMET, and the Γ-point NEVPT2 approach without embedding and find a decent agreement between the two.

Excited states of crystalline point defects with density matrix embedding theory

ACS Fall 2021

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