Density functional theory and Hartree-Fock-density functional theory calculations of 17O, 33S, and 73Ge quadrupole coupling constants

The performance of several density functional theory and Hartree-Fock density functional theory methods in conjunction with Pople type bases for the calculation of O-17, S-33, and Ge-73 quadrupole coupling constants in gaseous state molecules was investigated. Assessment of the several models was made by linear regression analysis of the calculated gradient of the molecular electric field versus the experimental nuclear quadrupole coupling constant (NQCCs). Calculations for oxygen on six molecules with the B3LYP/6-311++G(3df,3p) model yield a residual standard deviation of 0.057 MHz (1.4%); for sulfur on 12 molecules with the B3LYP/6-311G(3df,3p) model, 0.42 MHz (1.8%); and for germanium on nine molecules with the B3P86/6-311G(2d) model, 0.83 MHz (1.0%). In the case of germyl acetylene, our calculations indicate that the experimental NQCC reported some time ago by Thomas and Laurie [J. Chem. Phys. 44 (1966) 2602] was incorrectly assigned with respect to algebraic sign. Predictions are made of the O-17 and S-33 NQCCs in furan, 4H-pyran-4-one, 4H-pyran-4-thione, and 4H-thiapyran-4-thione; and of the Ge-73 NQCC in germyl bromide. (C) 2000 Published by Elsevier Science B.V.