Expressibility of comb tensor network states (CTNS) for the P-cluster and the FeMo-cofactor of nitrogenase

Polynuclear transition metal complexes such as the P-cluster and FeMo-cofactor of nitrogenase with eight centers represent a great challenge for current electronic structure methods. In this work, we initiated use comb tensor network states (CTNS), whose underlying topology has one-dimensional backbone several branches, many-body wavefunction ansatz to tackle these challenging systems. As an important first step, explored expressive power CTNS different topologies. To end, presented algorithm express configuration interaction (CI) into based on Schmidt decomposition. The was illustrated representing approximate CI wavefunctions obtained from selected calculations three chemically meaningful structures, which successively group orbitals belonging same atom branches. conventional matrix product (MPS) representation special case. We also discussed insights gained decompositions, shed some light future developments efficient numerical tools polynuclear complexes.