Ab initio calculations for bromine adlayers on the Ag(100) and Au(100) surfaces: the c(2x2) structure

Ab initio total-energy density-functional methods with supercell models have been employed to calculate the c(2x2) structure of the Br-adsorbed Ag(100) and Au(100) surfaces. The atomic geometries of the surfaces and the preferred bonding sites of the bromine have been determined. The bonding character of bromine with the substrates has also been studied by analyzing the electronic density of states and the charge transfer. The calculations show that while the four-fold hollow-site configuration is more stable than the two-fold bridge-site topology on the Ag(100) surface, bromine prefers the bridge site on the Au(100) surface. The one-fold on-top configuration is the least stable configuration on both surfaces. It is also observed that the second layer of the Ag substrate undergoes a small buckling as a consequence of the adsorption of Br. Our results provide a theoretical explanation for the experimental observations that the adsorption of bromine on the Ag(100) and Au(100) surfaces results in different bonding configurations.Comment: 10 pages, 4 figure, 5 tables, Phys. Rev. B, in pres

THE TEMPERATURE DEPENDENCE OF THE ANISOTROPY FIELD IN R2Fe14B COMPOUNDS (R = Y, La, Ce, Pr, Nd, Gd, Ho, Lu)

La variation thermique du champ d'anisotropie a été determinée dans les composés du type R2Fe14B (R = Th, Y, La, Ce, Pr, Nd, Gd, Ho, Lu) à des températures, entre 4.2 K et la température de Curie. Dans les composés Nd2Fe14B et Pr2Fe14B on a observé une réorientation du spin.The temperature dependence of the anisotropy field was measured in various compounds of the type R2Fe14B (R = Th, Y, La, Ce, Pr, Nd, Gd, Ho, Lu) at temperatures between 4.2 K and the Curie temperature. In Nd2Fe14B and Pr2Fe14B a spin reorientation was found to occur below room temperature

THE EFFECT OF SUBSTITUTION IN Nd2Fe14-xZxB (Z = Al, Si, Ga, Co, Ni) COMPOUNDS

Almost every element substituting Fe in Nd2Fe14B lowers the magnetocrystallined anisotropy. The effect on the ordering temperature Tc is different : in particular Al and Ni reduce Tc, whereas Si, Ga and Co increase Tc. Mössbauer experiments show that the Fe atoms are substituted in a non random manner. This is supported by the different magnetic properties due to the various substituents