Charge redistribution at Pd surfaces:Ab initiogrounds for tight-binding interatomic potentials

Abstract

A simplified tight-binding description of the electronic structure is often necessary for complex studies of surfaces of transition metal compounds. This requires a self-consistent parametrization of the charge redistribution, which is not obvious for late transition series elements (such as P d, Cu, Au), for which not only d but also s − p electrons have to be taken into account. We show here, with the help of ab initio FP-LMTO approach, that for these elements the electronic charge is unchanged from bulk to the surface, not only per site but also per orbital. This implies different level shifts for each orbital in order to achieve this orbital neutrality rule. Our results invalidate any neutrality rule which would allow charge redistribution between orbitals to ensure a common rigid shift for all of them. Moreover, in the case of P d, the power law which governs the variation of band energy with respect to coordination number, is found to differ significantly from the usual tight-binding square root. * The CRMC2 is also associated to the Universities of Aix-Marseille II and III.

Novel dynamic effects in electrocatalysis of methanol oxidation on supported nanoporous TiO2 bimetallic nanocatalysts

“…On the other hand, in several recent experimental studies [76,82,96,[119][120][121][122][123][124][125], a decrease in catalytic activity with particle size below ca. 3 nm has been observed indicating that increasing the surface area of nanoparticulate catalysts may not work in the limit of ultra small particles.…”

“…Studies of well defined monodisperse size-tunable core-shell nanoparticles [97][98][99][100][101][102][103][104][105][106][107][108][109][110][111] have shown that different kinds of size effects proliferate in the nanoworld and influence such different properties as light absorption [112], melting point [113], standard electrode potential [114], photoelectric yield [115,116], surface plasmon frequency [117,118], etc. The size effect in catalysis of methanol oxidation on ultrasmall nanoparticles Pt n (with size: 1-3 nm) has been attributed to the stronger binding of CO ad [76,82,96,[119][120][121][122][123][124][125] due to large surface strain [126] induced by high curvature of small nanoparticles and the resulting contraction of the lattice parameter, which may be as high as 5% [82]. A considerable change in chemisorption and catalytic properties may then likely result [126] from an upward shift in the d-band center, toward the Fermi level.…”

Different wavelength oscillations in the conductance of5dmetal atomic chains

“…The matrix elements h i,j,α,β , where i, j and α, β design sites and orbitals respectively, are taken from the fits to the chain and to the bulk ab-initio band structure. As a self-consistency condition we impose local charge neutrality by fixing the charge of the d orbitals and sp orbitals within the chain equal to the ones of the infinite chain [13]. The corresponding condition is also imposed on the electrodes surfaces.…”

Non‐reactive metal/oxide interfaces: from model calculations towards realistic simulations

“…The first solution yields [60]. In both cases, the proper treatment of sp-d hybridization thus leads to a dependence of the band term which is intermediate between square-root and pairwise.…”