•Interface to the GENNBO program of Weinhold and co-workers.•Absorption and CD spectra from time-dependent DFT or MR-CI. •Full Parallelization •Interface to graphics programs. •Some unique methods, in particular in the area of open-shells, spectroscopic parameters and MR-CI methods.•Efficient analytic frequencies for RI-DFT, hybrid DFT, Hartree-Fock and MP2 (also featuring QM/MM Hessians, ECPs, DKH/ZORA, van der Waals corrections etc., COSX and RI approximations).
Analytic gradients are also available (these methods were invented by the Grimme group). •Mulliken, Löwdin and Mayer analyses •Convenient breakdown of MO populations and easy to set up fragment analysis •Orbital localization via the Pipek-Mezey algorithm.
•Unrestricted natural orbitals and unrestricted corresponding orbitals.
ORCA is able to carry out geometry optimizations and to predict a large number of spectroscopic parameters at different levels of theory.
Besides the use of Hartee Fock theory, density functional theory (DFT) and semiempirical methods, high level ab initio quantum chemical methods, based on the configuration interaction and coupled cluster methods, are included into ORCA to an increasing degree.
it can be used together with the CASSCF module of ORCA.