AMMONIA ALANE

Ab initio studies employing basis sets approaching triple-zeta plus do uble-polarization plus f function quality are reported for AlH3 NH3, A lH3, and NH3. The self-consistent-field method was employed for all ba sis sets; the single and double excitation configuration interaction a nd the comparable coupled-cluster methods were utilized with a double- zeta plus polarization functions basis set. The dissociation energy of AlH3 NH3 is predicted to be 26 kcal/mol after correcting for zero-poi nt vibrational energy, in qualitative agreement with the rough estimat e of 30 kcal/mol by Haaland for Al-N bond strengths. In keeping with t he dative nature of the Al-N bond, the AlH3 and NH3 moieties do not un dergo larger changes upon the formation of AlH3 NH3. The resemblance o f AlH3 NH3 to the related compound BH3 NH3 is quite strong. The equili brium geometry, harmonic vibrational frequencies, infrared intensities , atomic charges, and dipole moment of ammonia alane are reported.