MULTIPLE-SCATTERED, RELATIVISTIC AND CORRELATED METHOD (MS-RC-XI) FOR MOLECULES

We have recently proposed a ''fully'' correlated relativistic local density method called RCXI method [M. Vijayakumar, N. Vaidehi, and M. S. Gopinathan, Phys. Rev. A 40, 6834 (1989)] for atoms and it has been shown that the results are of near Dirac-Hartree-Fock (DHF) accuracy. In this paper, the extension of the RCXI method to molecules by modifying the standard multiple-scattering Xalpha (MS-Xalpha) method is presented. Then, the modified method is applied to calculate various molecular properties such as the molecular correlation energy, the molecular orbital energy levels, the molecular orbital ionization energies, expectation value of 1/r, and magnetic property like isotropic shielding constant for atoms in molecules. Such calculations are made for several molecules including some of them containing heavy atoms. The calculated molecular properties are compared with the available experimental results and with results calculated by other methods. The effects of relativistic and correlation corrections on these molecular properties are discussed.