The spectroscopic constants and charge distribution for the ground sta
tes of 36 diatomic molecules containing C to F and Si to Cl atoms have
been studied with the deMon density functional program, using the loc
al density approximation and large basis sets. For each species, we co
mputed the energy and dipole moment at 13 or more internuclear separat
ions R. These energies were fitted to polynomials in R - R(e) by least
squares, with the value of R(e) determined by iteration. The extracte
d coefficients were used to compute spectroscopic constants. The avera
ge absolute deviations from experiment were found to be 0.0084 angstro
m for R(e), 29 cm-1 for omega(e), 1.11 cm-1 for omega(e)x(e), 0.59 x 1
0(-3) cm-1 for alpha(e), and 1.4 eV for D0. The net charges from Mulli
ken population analysis and the dipole moments for the heteronuclear d
iatomic molecules are discussed in relationship to the electronegativi
ties of the elements. The average absolute difference between mu(upsil
on=0)calc and mu(upsilon=0)obs is 0.15 D. Unusual charge distributions
were found in CF, NF, OF, CCl, NCl, and OCl.