ELECTRON CORRELATION AND RELATIVISTIC EFFECTS IN XENON TETRAFLUORIDE

Ab initio all-electron fully relativistic Dirac-Fock self-consistent field and Dirac-Fock-Breit calculations are reported for the XeF4 molecule at various internuclear distances assuming the experimental D4h geometry with our recently developed relativistic universal Gaussian basis set. The nonrelativistic limit Hartree-Fock calculations were also performed for XeF4 at various internuclear distances. The calculated relativistic correction to the total energy of molecule at the Dirac-Fock level is approximately -5856 eV, whereas the magnetic part of the Breit correction to the electron-electron interaction is calculated as approximately 177 eV. The electron correlation effects were included in the nonrelativistic Hartree-Fock calculations using the second-order Moller-Plesset (MP2) theory, and the calculated correlation energy for XeF4 is -71 eV. The basis-set superposition error (BSSE) was estimated by using the counterpoise method for Xe and F. The inclusion of both the relativistic and electron correlation effects in the calculated total energies of F, Xe, and XeF4 predicts the Xe-F bond length and dissociation energy of XeF4 as 1.952 angstrom and 5.59 eV, respectively, which are in excellent agreement with the experimental values of 1.953 angstrom and 5.69 eV, respectively, for XeF4. The contribution of the electron correlation and relativistic effects to the dissociation energy of XeF4 is 8.11 and 0.05 eV, respectively. The Breit interaction, however, contributes only 0.02 eV to the dissociation energy of XeF4. Electron correlation is most significant for the prediction of an accurate value of dissociation energy, whereas relativistic effects are very important for the prediction of spin-orbital splitting as well as the energies of the orbitals, especially the inner orbitals of XeF4. (C) 1995 John Wiley & Sons, Inc.