Dirac-Fock-Breit-Gaunt calculations for tungsten hexacarbonyl W(CO)(6)

摘要

The first all-electron fully relativistic Dirac-Fock-Breit-Gaunt (DFBG), Dirac-Fock (DF), and nonrelativistic (NR) Hartree-Fock (HF) calculations are reported for octahedral (O-h) tungsten hexacarbonyl W(CO)(6). Our DF and NR HF calculations predict atomization energy of 73.76 and 70.33 eV, respectively. The relativistic contribution of similar to 3.4 eV to the atomization energy of W(CO)(6) is fairly significant. The DF and NR energy for the reaction W + 6CO -> W(CO)(6) is calculated as -7.90 and -8.86 eV, respectively. The mean bond energy predicted by our NR and DF calculations is 142.5 kJ/mol and 177.5 kJ/mol, respectively, and our predicted DF mean bond energy is in excellent agreement with the experimental value of 179 kJ/mol quoted in the literature. The relativistic effects contribute similar to 35 kJ/mol to the mean bond energy and the calculated BSSE is 1.6 kcal/mol, which indicates that the triple zeta basis set used here is fairly good. The mean bond energy and the atomization energy calculated in our DFBG SCF calculations, which include variationally both the relativistic and magnetic Breit effects, is 157.4 kJ/mol and 68.84 eV, respectively. The magnetic Breit effects lead to a decrease of similar to 20 kJ/mol and similar to 4.9 eV for the mean bond energy and atomization energy, respectively, for W(CO)(6). Our calculated magnetic Breit interaction energy of -9.79 eV for the energy of reaction (Delta E) for W + 6CO -> W(CO)(6) is lower by similar to 1.90 eV as compared to the corresponding DF value (Delta E) and contributes significantly to the Delta E. A detailed discussion is presented of electronic structure, bonding, and molecular energy levels at various levels of theory for W(CO)(6). Published by AIP Publishing.