GEOMETRIES AND BOND-ENERGIES OF PHN AND PHN+ (N = 1-3)

All-electron complete active space self-consistent field (CASSCF) followed by full second-order configuration interaction (SOCI) calculations which included up to 1.7 million configurations have been made on several electronic states of PH(n) and PH(n)+ (n = 1-3). A comparison is made of the results of several basis sets up to the largest set, namely, the (13s10p3d2 f1g/7s6p3d2 f1g) basis set for P and a (l0s5pld/8s4pld) basis set for the hydrogen atom. Relativistic effective core potentials/CASSCF/multireference configuration interaction computations have also been carried out. The properties of three new excited states for PH3 have been computed as well as the experimentally observed X 1A1, 3A2', and 1A2' states. The calculated inversion barrier of PH3 is 34.6 kcal/mol whereas the corresponding inversion barrier of PH3+ is only 2.5 kcal/mol. The bond energies of PH(n) and PH(n)+ as well as adiabatic ionization energies of PH(n) are computed and compared with experimental results. The core-valence and core-external correlation effects are also computed for the diatomic PH molecule.