2014 Volume 13 Issue 1 Pages 43-49
We have developed an efficient direct spin-orbit configuration interaction (SOCI) program system with one-component L-S coupled configurations. To realize the high performance, we have employed various aspects of group theories. The formulas of coupling coefficients for the U (2n) generators were expressed in terms of segment values of GUGA. With the time reversal symmetry, we can define "real" spin functions for the even number of electrons system. The use of such spin-functions is essential to make the CI matrix real symmetric and also to facilitate the double point group applications. For the odd number of electrons system, we add a virtually non-interacting electron to make the total number of electrons even, enabling us to use the "real" spin functions for the real arithmetic, and keeping the high efficiency of computation.
