RELATIVISTIC 4-COMPONENT MULTICONFIGURATIONAL SELF-CONSISTENT-FIELD THEORY FOR MOLECULES - FORMALISM

A formalism for relativistic four-component multiconfigurational self- consistent-held calculations on molecules is presented. The formalism parallels a direct second-order restricted-step algorithm developed fo r nonrelativistic molecular calculations. The presentation here focuse s on the differences required by the use of the Dirac Hamiltonian with the incorporation of time-reversal symmetry and point group symmetry for D-2h and subgroups, providing the expressions in this framework wh ich correspond to the nonrelativistic expressions. It is found that an efficient algorithm requires only twice the memory used by the larges t nonrelativistic calculation in the equivalent basis, due to the comp lex arithmetic. The feasibility of the calculations is then determined more by the disk space for storage of integrals and N-particle expans ion vectors. (C) 1996 American Institute of Physics.