ORCA is an ab initio, DFT, and semi-empirical SCF-MO package developed by Frank Neese et al. at the Max Planck Institute for Chemical Energy Conversion.

The ORCA Input Library contains a collection of ORCA input that show you how to easily do various tasks using the many methods and approximations in the ORCA quantum chemistry code. The Library is built on the philosophy that it is usually faster to get a new calculation up and running by seeing some example input for a calculation and modifying it rather than writing new input from scratch (and looking up each keyword). The website is based on input files which are in a simple-as-possible format, i.e. using mostly the SimpleInput keywords and using the BlockInput only when necessary. Expert users will know how to switch between SimpleInput and BlockInput and one can look up the relevant block input settings in the ORCA Manual. There are also tips and tricks and general recommendations on computational chemistry

The Library is not a replacement for reading the ORCA Manual that contains much more theoretical detail about the many methods available in ORCA

ORCA 4.0 has finally been released. The site has been updated to be ORCA 4 compatible.

Any problems that occur when running ORCA calculations should be submitted to the ORCA Forum. The ORCA Forum is an interactive forum where users can post questions and report bugs. The ORCA Forum is run directly by members of the ORCA team.

Questions and comments regarding this site may be directed to Ragnar Bjornsson. E-mail

Ragnar Bjornsson (RB)
Tobias Kraemer (TK)
Manuel Sparta (MS)
Igor Schapiro (IS)
Jessica Barilone (JB)
Bradley D Rose (BDR)

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