COLUMBUS is a computational chemistry software suite for calculating ab initio molecular electronic structures, designed as a collection of individual programs communicating through files. The programs focus on extended multi-reference calculations of atomic and molecular ground and excited states. Besides standard classes of reference wave functions such as CAS and RAS, calculations can be performed with selected configurations. It makes use of the atomic orbital integrals and gradient routines from the DALTON program. The program is available free of charge under license (including the DALTON license).
COLUMBUS is frequently used for nonadiabatic problems because of its ability to calculate MRCI nonadiabatic coupling vector analytically.(Wikipedia)