Browsing by Author "ARRATIA-PEREZ, R"

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    CALCULATED PARAMAGNETIC HYPERFINE-STRUCTURE OF THE C2-UPSILON ISOMERS OF AG-3
    (1994) BRAVOVASQUEZ, JP; ARRATIA-PEREZ, R
    Dirac spin-restricted molecular orbital (DSW-X alpha) calculations on the two C-2v isomers of the matrix-isolated Ag-3 clusters using the Hedin-Lundqvist-Vosko-MacDonald relativistic local density exchange-cor relation potential are reported. The resulting ground-state cluster dirac wave functions are used through a relativistic first-order perturbation algorithm to model the paramagnetic hyperfine interactions of these bent isomers. The calculated isotropic and anistropic spin populations, and paramagnetic hyperfine interactions of the acute and obtuse isomers are in reasonable agreement with empirical and resolved paramagnetic resonance data of the Ag-3 clusters isolated on the C6D6 and N-2 solid matrices, respectively.
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    RELATIVISTIC ELECTRONIC-STRUCTURE OF STAGGERED AND ECLIPSED CONFORMATIONS OF OCTACHLORODIOSMATE(III)
    (1991) ARRATIA-PEREZ, R
    Symmetry-adapted angular momentum basis functions have been generated for the D4d* and D4h* molecular double point groups. These basis functions are used to obtain the relativistic molecular orbitals for the staggered (D4d) and eclipsed (D4h) rotameric geometries of octachlorodiosmate(III) via the self-consistent field Dirac Scattered-Wave (SCF-DSW) method. Double-point-group symmetry arguments and relativistic molecular orbital calculations for the Os2Cl8(2-) ions indicate that the molecular orbitals involving the sigma, pi, delta, and delta* metal-metal bond components remain nondegenerate in both conformations. Spin-orbit interaction splits the pi-bond component of both conformers by about 0.35 eV and removes the orbital degeneracy involving the delta and delta* bond components of the staggered conformer. Double-point-group arguments and the results of DSW calculations on the staggered conformer allow us to reassign the two lowest absorption bands seen in the visible spectrum as being primarily metal-metal based.
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    SPIN ORBIT EFFECTS ON RUO4 AND OSO4
    (1993) ARRATIA-PEREZ, R
    Dirac molecular orbital calculations on both molecules indicate that spin-orbit coupling splits the 2t2 and 3t2 MOs into the 2e'' + 2u' (2e'' > 2u') and 4u'+3e'' (4u'> 3e'') relativistic counterparts, due to the small metal contents of the nd3/2 and nd5/2 spinors, and of the (n + 1)p3/2 and (n + 1)p1/2 spinors, respectively. The unusual broad band E could be assigned to ionizations arising from a group of relativistic orbitals (3q, 2e3 and 2q) with significant nd5/2 and nd3/2 Metal contents. The calculated spin-orbit and valence bandwidth values are in good agreement with resolved PES data.
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    THE M6S8L6 CLUSTERS - AN EXAMPLE IN CLUSTER AND CONDENSED-PHASE CHEMISTRY
    (1993) ARRATIA-PEREZ, R
    Dirac molecular orbital calculations (DSW-Xalpha) on the octahedral molecular cluster models M6S8L6 (M=Mo, W; and L=two-electron ligand sigma donor) have been carried out. The calculated cluster valence density of states, valence bandwidth and calculated formal charge on each Mo atom, and calculated outer core spin-orbit parameters of the metal and S-facial atoms are in good accord with resolved XPS and UPS data of the molecular clusters Mo6S8 (PEt3) 6, W6S8 (PEt3)6, and of the solid AMo6S8 (A = Pb, Sn) superconducting ternary phases.