The structure of liquid carbon dioxide and carbon disulfide.

We present neutron and x-ray scattering data (a 2N+X experiment) of liquid CO(2) and CS(2) at a density of about 10 molecules/nm(3). Because the scattering length contrast of the carbon isotope is very small and, in fact, smaller than anticipated from standard scattering length tables, a direct partial structure factor determination via matrix inversion gives unconvincing results. Instead we search for the best representation of the three independent scattering data sets by a simulation of rigid molecules interacting via a 12-6-1 potential, furthermore restricting the pressure p, the density rho, and the temperature T to the experimental values. We show that a 12-6-1 potential is completely adequate to describe the structure of CO(2); for CS(2) we find that the best 12-6-1 potential still slightly overestimates the height of the sulfur-sulfur pair-distribution function g(SS). Orientational correlations reflect the similarities much more than the differences of the two molecular systems. The distinct differences in the atom-atom pair distribution functions of CO(2) and CS(2) do not mean that their structures are radically different and the comparison with the crystalline structures is somewhat deceptive. A linear transformation, wherein all the parameters describing the interaction and the geometry of CS(2) are changed to those of CO(2), allows us to point out the physical parameters which may be responsible for the differences or similarities in thermodynamic behavior (pressure) and structures (orientations) between the two liquids.

Structure of As(x)Te(100-x) (20

A systematic and detailed investigation of the structure of As(x)Te(100-x) glasses (20

'Wrong bonds' in sputtered amorphous Ge(2)Sb(2)Te(5).

The structure of sputtered amorphous Ge(2)Sb(2)Te(5) was investigated by high energy x-ray diffraction, neutron diffraction and Ge-, Sb- and Te K-edge EXAFS measurements. The five datasets were modelled simultaneously in the framework of the reverse Monte Carlo simulation technique. It was found that apart from Te-Sb and Te-Ge bonds existing in the crystalline phases, Ge-Ge and Sb-Ge bonding is also significant in sputtered amorphous Ge(2)Sb(2)Te(5). According to our results, all components obey the '8-N' rule.

Competition between order and phase separation in Au-Ni.

We have measured and theoretically analyzed the diffuse scattering in the binary alloy system Au-Ni, which has been proposed as a testing ground for theories of alloy phase stability. We found strong evidence that in the alloys Au3Ni and Au3Ni2, fluctuations of both ordering- and clustering-type are competing with each other. Our results resolve a long-standing controversy on the balance of relaxation and mixing energies in this alloy system and explain recent findings of ordering in thin Au-Ni films.

Strain-induced nonanalytic short-range order in the spin glass Cu(83)Mn(17).

We present a theoretical and experimental study of the effect of lattice distortions on the short-range order and the energetics of ordering binary alloys. Applying a reciprocal space approach which accounts for the elastic response of the lattice, the diffuse scattering of the model system Cu(83)Mn(17) can be explained with only a few physical parameters. The model calculations point to a nonanalytic diffuse intensity at q = 0. X-ray scattering experiments are presented providing clear evidence for this phenomenon which carries detailed information on the strain-induced interaction.