Symmetry in spin-orbit coupling

A thorough review of the symmetry properties of the spin-orbit coupling operator and its matrix elements is presented. Various consequences of symmetry upon the practical calculations of spin-orbit coupling matrix elements at both point and double group level are illuminated. A parallelisation scheme and various steps unrelated to symmetry toward making the calculations more efficient are discussed. Tests of scalability of the code as implemented into the distributed version of GAMESS are presented.