Block2: a comprehensive open source framework to develop and apply state-of-the-art DMRG algorithms in electronic structure and beyond

TL;DR

Block2 is an open source framework that provides flexible, efficient, and extensible implementations of advanced DMRG algorithms for electronic structure calculations and beyond, supporting various quantum chemistry extensions.

Contribution

It introduces a comprehensive, open source framework with optimized, extensible DMRG algorithms tailored for electronic structure and quantum chemistry applications.

Findings

Supports multiple DMRG algorithms out-of-the-box

Includes optimizations for electronic structure Hamiltonians

Demonstrates versatility across various applications

Abstract

Block2 is an open source framework to implement and perform density matrix renormalization group and matrix product state algorithms. Out-of-the-box it supports the eigenstate, time-dependent, response, and finite-temperature algorithms. In addition, it carries special optimizations for ab initio electronic structure Hamiltonians and implements many quantum chemistry extensions to the density matrix renormalization group, such as dynamical correlation theories. The code is designed with an emphasis on flexibility, extensibility, and efficiency, and to support integration with external numerical packages. Here we explain the design principles and currently supported features and present numerical examples in a range of applications.