{LOCAL-DENSITY STUDIES OF DIATOMIC AB MOLECULES, A

The spectroscopic constants and charge distribution for the ground states of 36 diatomic molecules containing C to F and Si to Cl atoms have been studied with the deMon density functional program, using the local density approximation and large basis sets. For each species, we computed the energy and dipole moment at 13 or more internuclear separations R. These energies were fitted to polynomials in R - R(e) by least squares, with the value of R(e) determined by iteration. The extracted coefficients were used to compute spectroscopic constants. The average absolute deviations from experiment were found to be 0.0084 angstrom for R(e), 29 cm-1 for omega(e), 1.11 cm-1 for omega(e)x(e), 0.59 x 10(-3) cm-1 for alpha(e), and 1.4 eV for D0. The net charges from Mulliken population analysis and the dipole moments for the heteronuclear diatomic molecules are discussed in relationship to the electronegativities of the elements. The average absolute difference between mu(upsilon=0)calc and mu(upsilon=0)obs is 0.15 D. Unusual charge distributions were found in CF, NF, OF, CCl, NCl, and OCl.