A density functional study of the structures and ionization energies of some scandium compounds with hydrogen and oxygen

The geometries, frequencies and energies of various Sc species with hydroge n and oxygen which might exist in a flame doped with Sc were studied with d ensity functional methods. Two functionals, B3LYP and BP86, equipped with t wo basis sets, TZVP and 6-311 + +G(3df,3pd), were employed. In predicting g eometries and frequencies, the BP86 functional performs consistently better than does the B3LYP functional, but the B3LYP functional performs better f or energy calculations. For most species, the effects of using different ba sis-set effects are minor. The calculated ionization energies of 6.47 eV fo r Sc and 6.6 eV for ScO are in good agreement with the experimental values of 6.561 for Sc and 6.6 +/- 0.3 eV for ScO. For other species, suggested va lues of the calculated ionization energies are 6.3 eV for ScH, 6.1 for ScOH , 9.3 for HScO, 6.5 for HScOH, 9.5 for OScOH, 6.2 for Sc(OH)(2), 9.6 for HS c(OH)(2) and 10.1 eV for Sc(OH)(3), all with an approximate error of 0.2-0. 3 eV. These high values indicate that the formation of Sc-containing ions i n flames by thermal (collisional) ionization is unlikely. (C) 2001 Elsevier Science BN. All rights reserved.