Starting from the GRASP2K version by Jönsson et al. CPC 177, 7 (2013) and the -published there- relativistic configuration interaction (RCI) program, I developed a new RCI program, which is based on perturbation theory and uses zero- and first-order wavefunction spaces. The first-order space is divided into two or more subspaces, and each of these subspaces contain wavefunctions that are optimized based on different Partition Correlation Functions (PCFs). The latter are Configuration State Functions (CSFs) that are generated by allowing substitutions of electrons to correlation orbitals according to specified rules. Applying these rules results in PCF spaces that capture different electron correlation effects.
The main strength of this method is that ...