The PSI3 suite of quantum chemical programs is designed for efficient, high-accuracy calculations of properties of small to medium-sized molecules. The package's current capabilities include a variety of Hartree-Fock, coupled cluster, complete-active-space self-consistent-field, and multi-reference configuration interaction models. Molecular point-group symmetry is utilized throughout to maximize efficiency. * Arbitrarily high angular momentum levels in integrals and derivative integrals. (Up to k-type functions have been tested.) * Coupled cluster methods including CCSD and CCSD(T) with RHF, ROHF, UHF, and Brueckner orbitals. * Determinant-based CI including CASSCF, RAS-CI, and Full CI. * Multithreaded integral-direct SCF, MP2, and MP2-R12. * Excited state methods: CIS, CIS(D), RPA, and EOM-CCSD. * Analytic energy gradients for CCSD with RHF, ROHF, and UHF orbitals. * Coupled cluster linear response methods for static and dynamic polarizabilities and optical rotation. * Diagonal Born-Oppenheimer correction (DBOC) for RHF, ROHF, UHF, and CI wave functions.