One‐electron properties of several small molecules calculated using the local density approximation within density functional theory

Quadrupole moment function and absolute infrared quadrupolar intensities for N2

High level ab initio methods have been used to calculate values of the quadrupole moment of the ground X (1)Sigmag+ state of N2 on a dense radial mesh spanning the interval of 0.8-12.1 a.u. Detailed convergence tests indicate that the resulting equilibrium values of the quadrupole moment Theta(e)=-1.1273 a.u. and its first radial derivative dTheta(R)/dR/e=0.9604 a.u. have absolute uncertainties of 0.3% and 0.8%, respectively, and are more accurate than the best experimental values of these quantities. The calculated quadrupole moment function, together with a recently reported accurate analytic empirical potential energy function [Le Roy et al., J. Chem. Phys. 125, 164310 (2006)], is used to generate values of the radial matrix elements determining the absolute intensities of infrared vibration-rotation transitions of ground-state N2, which take full account of vibration-rotation interactions. These results should improve the reliability of the interpretations of N2 contributions to infrared atmospheric spectra.

Density-functional calculation of core-electron binding energies of glycine conformers

Our recent procedure of computing accurate core-electron binding energies (CEBEs) with density-functional theory is applied to glycine conformers in this work. The procedure uses the unrestricted generalized transition-state model and a combined functional of Becke's 1988 exchange with Perdew's 1986 correlation. When a large basis set such as Dunning's correlation-consistent polarized valence quadruple zeta set is used, the average absolute deviation from experiment for the CEBEs of the most stable conformer of glycine is only 0.2 eV, compared with 18 eV for Koopmans' theorem. Key words: core-electron binding energies, density-functional theory, glycine.