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.
First, please register at the ORCA website.
A confirmation e-mail will be sent to you. Please follow the instructions.
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.