KOHN-SHAM CALCULATIONS ON OPEN-SHELL DIATOMIC-MOLECULES

We report density functional theory calculations of bond-lengths, freq uencies and dissociation energies for a number of open-shell diatomic molecules. Our calculations were performed with very accurate quadratu re for three distinct forms of the exchange-correlation functional: S- VWN, B-P86-VWN and B-LYP. We find good agreement between experiment an d theory for equilibrium bond lengths and harmonic frequencies. The de nsity functional theory methods represent a significant improvement in cost and accuracy over the restricted and unrestricted Moller-Plesset techniques. We compare the relative performance of the different func tionals and conclude that the gradient corrected functionals give sign ificantly better frequencies and dissociation energies than the local density approximation (S-VWN). Kohn-Sham density functional theory cal culations were performed in both the unrestricted Kohn-Sham and restri cted Kohn-Sham formalisms.