On the relative abundance and interconversion of the two lowest isomers of AlP3

The relative abundance of the two lowest and energetically close singlet states of AlP3 (C2V and CS symmetries) is studied using second-order Møller–Plesset perturbation theory, MP2/aug-cc-pVTZ, and density-functional theory, B3LYP/aug-cc-pVTZ, calculations. The C2V ↔ CS barrier is calculated to be around 30 kcal/mol precluding possible interconversion. Gibbs free energy calculations indicate that the C2V form is more stable for all temperatures considered (80 K < T < 320 K). For temperatures below 150 K (supersonic expansion conditions) the relative abundance of the C2V is larger than 90% indicating that upon cold formation experimental results will refer almost exclusively to the C2V isomer.