CASPT2 study on HAlN and HNAl radicals

The nine-valence-electron HAlN and HNAl radicals have been studied for the first time by large-scale theoretical calculations using CASSCF and CASPT2 methods in conjunction with the contracted atomic natural orbital (ANO) basis sets. The ground and lowest excited states of HAlN and HNAl were investigated. The possible unimolecular conversions between the low-lying states of HAlN and HNAl were discussed. The calculated results indicated that the ground-state HAlN is linear, while the ground-state HNAl is bent, which is in contradiction to Walsh’s rules predicting linear structures for the HXY systems containing 10 or less valence electrons.