ORCA is a modern electronic structure program package for quantum chemistry with specific emphasis on spectroscopic properties of open-shell molecules.
The binaries of ORCA are available free of charge for academic users for a variety of platforms.
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You can study the ORCA manual, while you download and install ORCA (you must be logged in, in order for the download links to appear).
Windows users: please download the most recent "Windows Binaries Version" available. Create a new folder named "Orca" wherever you prefer, and unzip the compressed binary files to it.
ORCA is mainly used to generate UV Vis absorption spectra of lanthanide complexes.