The CheMPS2 library provides a free open-source spin-adapted implementation of the density matrix renormalization group (DMRG) for ab initio quantum chemistry. This method allows to obtain numerical accuracy in active spaces beyond the capabilities of full configuration interaction. For the input Hamiltonian and targeted symmetry sector, the library performs successive DMRG sweeps according to a user-defined convergence scheme. As output, the library returns the minimal encountered energy as well as the 2-RDM of the active space. The latter allows to calculate various properties, as well as the gradient and Hessian for orbital rotations or nuclear displacements.
This is a companion discussion topic for the original entry at https://copr.fedorainfracloud.org/coprs/talcite/CheMPS2/