Chapter 6 - Post-density matrix renormalization group

Abstract

Ab initio density matrix renormalization group (DMRG) method is well established and has become one of the most accurate numerical methods for the precise electronic structure solution of large active spaces. In the past few years, to capture the missing dynamic correlation, various post-DMRG approaches have been proposed through the combination of DMRG and multireference quantum chemical methods or density functional theory (DFT). However, problems also arise in the use of ab initio DMRG and post-DMRG methods to the “real-world” chemistry applications because of the improper description of the strongly correlated subsystem’s chemical environment (e.g., a solvent environment or biological metalloenzyme’s backbone). In this chapter, we first introduce the fundamentals for multireference quantum chemical calculations. Then, we discuss various post-DMRG approaches through DMRG’s integration with multireference configuration interaction, multireference perturbation theory, multireference coupled cluster, as well as DFT. Finally, treatments for describing embedded chemical environment are introduced and a summary and outlook is given.