ملخص: The properties of the diatomic thiophosphorus radical PS and its cation and anion, in their ground electronic states, are studied using UHF, RHF, ROHF, GVB and MP2 ab initio methods with the STO-3G*, 3-21G*, 6-31G and 6-31G* basis sets. As expected, the STO-3G* basis set is insufficient for the anion (outer molecular orbitals unbound). Most of the results obtained with the 6-31G basis set are unsatisfactory. In contrast, the equilibrium internuclear distances (re) obtained for the PS radical in all the ROHF and GVB optimizations with the 3-21G* and 6-31G* basis sets are satisfactory, the values ranging from 0.5 to 1.8% less than the best experimental value. The results indicate that re(PS(1+) X1[Sigma]+) and re(PS(1-) X3[Sigma]-) should be very close to 1.84 A and 2.04 A, respectively. The reliability of the MP2 results varies: [omega]e for the radical and the cation are 42% higher and 6% lower than the experimental frequencies, respectively. Thus MP2 computations on these species are not warranted. The dissociation energy for PS X2[Pi]r, obtained by both the GVB(3)/6-31G*(5d) and (6d) computations is De = 5.0 eV, about 10% higher than the mass spectral value, De = 4.6 +/- 0.1 eV. For the negative ion the computed electron affinity and dissociation energies predict that it is stable and should be observable under suitable conditions.

لغة: إنجليزية