Purpose: electronic Structure Calculations Latest version: 4.0.0 License: Mixed - Free for academics; forbidden for commercial. Website: https://orcaforum.cec.mpg.de/
ORCA is a program that implements HF, DFT, semi-empirical, and high level ab initio (CI and CC) methods with gaussian basis sets for electronic structure calculations.
ORCA implements a variety of standard quantum chemistry methods, but is especially tailored at geometry optimisation and prediction of spectroscopic parameters in open-shell molecular systems. It can be coupled to Gromacs for QM/MM calculations.