Spectroscopic properties of mixed gallium arsenide tetramers:: GaAs3±, GaAs3, Ga3As±, and Ga3As

Spectroscopic properties of the low-lying electronic states of Ga3As, As3Ga, and their anions and cations are computed by the complete active-space self-consistent field (CASSCF) followed by multireference singles+doubles configuration interaction (MRSDCI) calculations that included up to 4.4 million configurations. Whereas the ground state of Ga3As is found to be a symmetric triangular pyramidal (C-3v) (1)A(1) structure, the ground state of As3Ga is predicted to undergo Jahn-Teller distortion to a C-s (1)A(') state with a folded geometry. The ground state of the Ga3As- ion is found to be surprisingly a planar (C-2v) structure but the ground state of the GaAs3- ion exhibits a C-s nonplanar Jahn-Teller distorted geometry. The energy separations of a number of excited electronic states have been computed to predict the spectra of these species. The equilibrium geometries, vibrational frequencies, atomization energies, adiabatic ionization potentials, electron affinities, and other properties for the electronic states of Ga3As and As3Ga are computed and discussed. Large differences in the equilibrium geometries of the Ga3As- anion and the neutral Ga3As are predicted to result in considerable vibrational progression the anion photoelectron spectra. (C) 2001 American Institute of Physics.