Theoretical study of the low lying states of Ga2X (X = P, As)
Résumé
Since the low lying electronic states of Ga2X (X = P, As) are nearly degenerate, an accurate determination of the electronic structure of these states was incomplete in the previous works. In this study, the geometry optimization and vibrational frequency calculation have been performed at the various levels of theory, using the effective core pseudopotentials of the Ga and As atoms and the associated cc-pVTZ basis sets. The ground state of Ga 2P is found to be the 2A state correlating with the 2B2 state in C2v structure, which lies 0.031 eV above the global minimum at the RCCSD(T) level. The equilibrium of the 2A1 state is optimized above that of the 2B2 state, and the 2B1 state, predicted previously as the ground state, has a stable minimum above the optimized geometries of the former states. Concerning the low lying states of Ga2As, our results confirm in general the previous studies. Because all the states of both compounds can be considered monoconfigurational around their equilibrium, the RCCSD(T) method is well adapted to acurrately describe both systems. In turn, we have applied our obtained information to analyze the Ga2P- and Ga2As- anion photoelectron spectra, to which it remains difficult to appropriately assign the low lying states of Ga2P and Ga2As. As a consequence, our analysis supports the previous assignment for Ga2P, but contrasts partially to that for Ga2As. © 2010 American Chemical Society.