A Dirac–Fock self‐consistent field method for closed‐shell molecules including Breit interaction

We present a method for including the Breit interaction in relativistic self‐consistent field calculations for closed‐shell molecular systems using atomic basis spinors of kinetically balanced Gaussian‐type functions. The method extends the formalism described in a previous paper [A. Mohanty and E. Clementi, Int. J. Quantum Chem. 39 , 487–517 (1991)] that dealt with the two‐electron effect due to Coulomb interaction only. It is shown that both frequency‐dependent and frequency‐independent Breit interactions can be treated on equal footing, and the corresponding matrix elements are evaluated following the well‐known Fourier transform technique applied to electron repulsion integral evaluation in nonrelativistic molecular calculations.