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Based on results from density-functional calculations we present an interesting and unusual mechanism for a structural change in a certain class of intermetallic compounds that can be induced through hydrogen absorption. Through an atomic rearrangement, palladium-rich intermetallic compounds MPd (M = Mg, In, Tl) can change the structure from a tetragonal ZrAl or TiAl type to a cubic AuCu type structure. Within the density-functional calculations we study a possible reaction pathway via a gliding of atomic layers with and without the presence of hydrogen. Subsequently, we argue that H-Pd interactions can be held responsible for the structural change upon hydrogen uptake, and that entropic and packing effects can explain the existence of the lower-symmetric structures in the absence of hydrogen. [ABSTRACT FROM AUTHOR]

Results of a theoretical study of the properties of Sin, Gen, and SinGen clusters are presented. An approximate density-functional method in combination with genetic algorithms have been used in an unbiased determination of the structures of the lowest total energy. The resulting structural, energetic, and electronic properties are analysed and compared with each other for the different systems. [ABSTRACT FROM AUTHOR]

Abstract: We present a combined experimental (angle resolved photoemission: ARUPS) and theoretical study of the Shockley-type surface state in the L-gap of the (111)-face of Au covered with one monolayer of Ar. As known also from other systems consisting of rare-gas monolayers on noble metal (111) surfaces, the adsorbed rare-gas shifts the Shockley-state towards the Fermi level and increases the spin–orbit splitting, whereas the effective band mass remains unchanged. We analyze the observed changes by a comparison with ab initio slab-layer calculations based on the density functional theory (DFT), both within the local density approximation (LDA) and the generalized gradient approximation (GGA). Although the attractive van der Waals interaction between rare-gas and substrate is not properly considered in DFT there are considerable hybridization effects which allow to describe such weakly bound adsorbates quantitatively. We show to what extent the various DFT calculations correspond to the experimental results. Furthermore, we discuss the importance of lattice relaxation and the exact absorption position into the calculations. [Copyright &y& Elsevier]