Q. When do we use the SAC-CI general-R method?

 

A. The SAC-CI SD-R method is appropriate for ordinary single-electron excitation, ionization, and electron-attachment processes. In the SAC-CI general-R method, the order of the excitations operator is generalized upto higher-order excitations. Current SAC-CI program can include the excitation operators (R-operators) upto sextuple excitations. The general-R method is appropriate for multi-electron processes like two-electron excited states and shake-up ionizations.