A b i n i t i o theoretical study of arsine and trimethylgallium: The formation of GaAs by a stable adduct

Theoretical calculations for the closed-shell ground state of arsine (AsH3), trimethylgallium (TMG) [Ga(CH3)3], and the arsine–TMG adduct [H3As⋅Ga(CH3)3] are carried out at the self-consistent field (SCF) Hartree–Fock level of theory. In addition, the SCF results are compared with theoretical predictions obtained at the coupled cluster level of theory including all single and double excitations (CCSD). The equilibrium structure of arsine is found to be of C3v symmetry, while TMG and the adduct are found to be of C3 symmetry. Ab initio calculations are also performed on D3h gallane (GaH3) and the gallane–arsine adduct (H3Ga⋅AsH3) of C3v symmetry. The adduct binding energies and vibrational frequencies (SCF) are also obtained resulting in two stable bonded adduct species—arsine⋅TMG and arsine⋅gallane. Finally, our theoretical predictions support a slightly exothermic gas-phase reaction yielding GaAs through a TMG⋅AsH3 adduct which is formed without an activation barrier.