Update 8 July 2017: Please note that the latest version of Orca (4.0) uses a slightly different format for basis set and ECP assignment. Check the Orca Forum, Orca Input Library, or the Orca 4.0 manual for more information.
This is a very quick post on how to run a calculation in Orca. In this case, it is an optimization of the iridium pentachloronitrosyl anion. This was a post that I wrote for my research group to encourage the use of Orca for quantum mechanical calculations. I will write this up further in due course.