Heats of formation for AlH, AlOH, OAlH and OAlOH and their monocations

Heats of formation for AlH, AlOH, OAlH, and OAlOH molecules and their monocations are determined at the B3LYP, B3PW91, mPW1PW91 and B1LYP levels of density functional theory in conjunction with a series of extended basis sets, and at the G3, G3B3, CBS-Q and CBS-QB3 levels of the ab initio molecular orbital theory. Heats of formation were calculated from total atomization energies and from isodesmic reaction energies. The B3LYP hybrid leads to the most reliable results of the four tested functionals. However, ab initio model chemistry computations give more accurate heats of formation. The best values obtained for AM, AlOH, OAlH, OAlOH are 57.5, -46.4, -8.9 and -94.0 kcal mol(-1). Our results call into question recent estimations for OAlH and OAlOH. A kinetic modeling calculation for the formation of AlOH and OAlH isomers from recombination of H atoms with AlO radicals is reported. For AlH+, AlOH+, OAlH+ and OAlOH+ the values 251.1, 162.2, 245.0 and 132.9 kcal mol(-1) are predicted. Structural properties, harmonic vibrational frequencies, mode assignations and infrared intensities for all species are presented. (C) 2002 Elsevier Science B.V. All rights reserved.