Chemps2 is a scientific library which contains a spin-adapted implementation of the density matrix renormalization group (DMRG) for ab initio quantum chemistry. This method allows one to obtain numerical accuracy in active spaces beyond the capabilities of full configuration interaction (FCI).

For an 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 second order reduced density matrix (2-RDM) of the active space. With the latter, various molecular properties can be calculated, as well as the gradient and Hessian for orbital rotations or nuclear displacements. In addition, several correlation functions can be obtained to investigate the electronic structure in the active space.

This package installs the library for Python 2.