Block2: an open-source library that extends the boundary of the application of ab initio density matrix renormalization group methods*

In this talk I will summarize our recent efforts on the development of an open-source ab initio density matrix renormalization group (DMRG) implementation called block2, which is focused on the easy combination of the highly accurate and scalable DMRG methods with other electronic structure methods such as CCSD, DMET, DMFT, MRCI, and MRPT. The application of this code ranges from high dimensional Heisenberg and Hubbard model simulations, transport property of single impurity Andersen model, and twisted bilayer graphene models, to ab initio simulations for chromium dimer, iron-sulfur catalytic cluster, Kondo problem, and high temperature superconductivity. We found that the connection among different theories is the key to making the expensive ab initio DMRG a unique and practical tool for understanding challenging real-world problems.