Theoretical study of the low lying states of Al2As: Towards a reliable description

Recently the 2A′ ground state has been reported for Ga2P and Ga2As [7], however, there is no previous work on the Cs structure state of Al2As. This Letter reports the geometry optimisations and vibrational frequency calculations performed, using various approaches. In this study, the global minimum belongs to the 2A′ state, correlating with the 2B2 state. The 2A1 state is also reported for the first time. Difficulties in treating the 2B2 state are discussed in terms of the Hartree–Fock instability. Based on our calculations, we discuss the Al2As− photoelectron spectrum.