Electronic states of Ga(3)Si, GaSi(3), and their ions.

The equilibrium geometries and electronic states of Ga(3)Si, GaSi(3), and their ions are investigated using the complete active space self-consistent-field (CASSCF) and DFT(B3LYP)/CCSD(T) techniques. The (2)B(1), (3)B(1), and (1)A(1) states in C(2v) symmetry with a planar quadrilateral geometry are found to be the ground states of Ga(3)Si, Ga(3)Si(+), and Ga(3)Si(-), respectively. On the other hand, the ground states of GaSi(3), GaSi(3)(-) are also predicted to undergo Jahn-Teller distortion to the (2)A'' and (1)A' states in C(s) with a distorted triangular pyramid geometry, respectively, whereas that of GaSi(3)(+) is found to be the (1)A(1) state in C(3v) with symmetric triangular pyramid structure. Binding energies, electron affinities, ionization energies of Ga(3)Si and GaSi(3) are computed at the CCSD(T)/QCISD(T) level and discussed.