arXiv subjects
Publications and source records attributed to T. Vogt.
Many crystalline materials show chemical short range order and relaxation of neighboring atoms. Local structural information can be obtained by analyzing the atomic pair distribution function (PDF) obtained from powder diffraction data. In this paper, we present the successful extraction of chemical short range order parameters from the x-ray PDF of a quenched Cu_3Au sample.
The structure of LiMoS2 has been experimentally determined for the first time. The approach of atomic pair distribution function (PDF) analysis was used because of the lack of well defined Bragg peaks due to the short structural coherence (~ 50 A) in this intercalation compound. This represents one of the first instances where the structure of such poorly diffracting material was determined from the total scattering including diffuse as well as Bragg scattering. The reduction of Mo by Li results in Mo-Mo bonding with the formation of chains of distorted Mo-S6 octahedra. Using the refined structural parameters the electronic band-structure for this material has been calculated and is in good agreement with observed material properties.
The lattice parameters of MgB2 up to pressures of 8 GPa were determined using high-resolution x-ray powder diffraction in a diamond anvil cell. The bulk modulus, B0, was determined to be 151 +-5 GPa. Both experimental and first-principles calculations indicate nearly isotropic mechanical behavior under pressure. This small anisotropy is in contrast to the 2 dimensional nature of the boron pi states. The pressure dependence of the density of states at the Fermi level and a reasonable value for the average phonon frequency account within the context of BCS theory for the reduction of Tc under pressure.