Theoretical prediction on low-lying states of HAlP and HPAl radicals

The HAlP and HPAl radicals have been studied using CASSCF, CASPT2, and CCSD(T) methods. The geometries of the stationary points were optimized at the CASPT2/ANO and CCSD(T)/aug-cc-pVTZ levels. For the double states, the potential energy curves of isomerization reactions between HAlP and HPAl were calculated as functions of HAlP bond angle. The calculated results showed that the ground-state HAlP is linear, while the ground-state HPAl is bent, which is in contradiction to Walsh’s rules predicting linear structures for the HXY systems containing 10 or less valence electrons. Some quartet states of HAlP and HPAl were also calculated.