Electronic States of Al 3 As 2 , Al 3 As 2 - , Al 3 As 2 + , Al 2 As 3 , Al 2 As 3 - , and Al 2 As 3 +

We have computed the optimized geometries and energy separations for the electronic states of Al 3 As 2, Al 2 As 3, and their positive and negative ions using complete active-space MCSCF (CASSCF) followed by multireference singles + doubles configuration interaction (MRSDCI) calculations which included up to 3.9 million configurations. The 2 A 1 ( C 2 v ) state is the lowest electronic state of Al 3 As 2 among seven states with distorted trigonal bipyramid structures. The 2 A 1 state and another distorted 2 B 1 ( C 2 v ) state are formed from the undistorted 2 E‘ and 2 E‘ ‘( D 3 h ) states, respectively, as a consequence of Jahn−Teller effect. The 2 A 2 ‘ ‘( D 3 h ) state is found to be the ground state of Al 2 As 3 with an undistorted trigonal bipyramid structure ( D 3 h ). Four electronic states of Al 3 As 2 + and Al 2 As 3 + were computed and their ground states are undistorted 3 A 2 ‘ and 1 A 1 ‘( D 3 h ) states for Al 3 As 2 + and Al 2 As 3 +, respectively. The 1 A 1 ‘( D 3 h ) state is the ground state for both Al 3 As 2 - and Al 2 As 3 - . The atomization energies, adiabatic ionization potentials, and other properties for the electronic states of Al 3 As 2 and Al 2 As 3 and a comparison with the Ga analogues are provided. The Al 3 As 2 cluster is shown to differ from Ga 3 As 2 in some states due to a greater charge transfer from Al(3s) to As(4p) in Al 3 As 2.