A DENSITY-FUNCTIONAL STUDY OF SC-2 AND SC-3

Density functional theory, using a gradient-corrected exchange-correla tion functional, has been applied to determine the equilibrium propert ies of various spin states of the Sc-2 and Sc-3 molecules. The ground state of Sc-2 is predicted to be (5) Sigma(u)(-) with R(e) = 2.64 Angs trom, omega(e) = 222 cm(-1) and D-e = 0.92 eV, followed by the (3) Sig ma(u)(-) and (1) Sigma(g)(+) states. The equilibrium structure of the (2)A(1)' ground state of Sc-3 is found to have D-3h symmetry with a bo nd length of 2.83 Angstrom. The calculated harmonic frequencies are 27 2 cm(-1) (a(1)') and 153 cm(-1) (e'), while the atomization energy is 2.49 eV, Several low-lying excited states of Sc-3 are found to lie abo ut 0.2 eV above the ground state. The predicted ground states of Sc-2 and Sc-3 and their vibrational frequencies are in accordance with the findings of ESR and resonance Raman studies. (C) 1997 Elsevier Science B.V.