PNNL

Abstract

Embedding theories became important approaches used for accurate calculations of both molecules and solids. In these theories a small chosen subset of orbitals is treated with an accurate method, called impurity solver, capable of describing higher correlation e ects. Ideally, such a chosen fragment should contain multiple orbitals responsible for chemical and physical behavior of the compound. Handing a large number of chosen orbitals presents a very signi cant challenge for the current generation of solvers used in the physics and chemistry community. Here, we develop a Green's function coupled cluster singles doubles and triples (GFCCSDT) solver that can be used for a quantitative description in both molecules and solids. This solver allows us to treat orbital spaces that are inaccessible to other accurate solvers. At the same time GFCCSDT maintains high accuracy of the resulting self-energy. Moreover, in conjunction with GFCCSD solver, it allows us to test the systematic convergence of computational studies. Developing the CC family of solvers paves the road to fully systematic Green's function embedding calculations in solids. In this paper, we focus on investigation of GFCCSDT self-energies for a strongly correlated problem of SrMnO3 solid. Subsequently, we apply this solver to solid MnO showing that an approximate variant of GFCCSDT is capable of yielding a high accuracy orbital resolved spectral function.