No abstract

The CuX and Cu 2 X series (X ) O, S, Se, Te, Po) have been investigated using a standard pseudopotential and a correlation-corrected pseudopotential for copper. Using the latter pseudopotential leads to cheaper but nevertheless accurate results in comparison to standard high-level ab initio methods. The spectroscopic parameters also compare favorably with the available experimental data. These calculations constitute the first theoretical study of Cu n Te and Cu n Po (n ) 1, 2). Trends in structural and energetic properties for the whole series are discussed, in particular the d 10 -d 10 "metallophilic interaction" between the copper atoms.

A systematic study of the singlet and triplet PXH2 potential energy surfaces, X ranging from nitrogen to bismuth, has been undertaken through a b initio methods. Geometries were optimized at the Hartree-Fock level, and single-point energies taking into account the electron correlation effects were calculated. Effective core potentials, including the main relativistic effects, have been used for the heaviest X atoms, i.e. arsenic, antimony, and bismuth. General trends in the structural and energetic properties of the various isomers, when going down group 15, are given. The possibility of forming P-Sb and P-Bi double bonds is c o n f i i e d , as the trans HPSbH and HPBiH isomers are found to be global minima on the singlet potential energy surfaces.The H2PSb and HZPBi isomers in their triplet states appear to be lower in energy than the corresponding trans (closed-shell) isomers, by 0.8 and 7.5 kcdmol, respectively. However, the energy barriers are large enough to prevent any isomerization of the HP-BiH species to HzPBi singlet or triplet species. On the other hand, the thermodynamic stability of the P-X double bond is predicted to decrease when X varies from nitrogen to bismuth, which can explain the difficulties encountered by the experimentalists to synthesize compounds containing P=Sb and P=Bi double bonds.