AN EFFICIENT IMPROVEMENT OF THE STRING-BASED DIRECT SELECTED CI ALGORITHM

A modified version of the Direct Selected Configuration Interaction Us ing Strings (DISCIUS) code is presented. From a series of test calcula tions it is shown that the string-based direct-CI algorithm is also ve ry efficient in larger examples than the ones we showed in our former version. The performance of this new code with respect to the computer time is reasonable as well as its storage requirements. Hence, we pre sent a new tool able to treat more than 10(6) determinants of a variat ional space that does not have a defined structure, i.e. a selected or any way truncated CI.