Anomalous thermal contraction of the first coordination shell in metallic alloy liquids.

Except for a few anomalous solids and liquids, materials expand upon heating. For liquids, this should be reflected as a shift in the peak positions in the pair correlation function, g(r), to higher r. Here, we present the results of a detailed study of the volume thermal expansion coefficients and the temperature dependences of g(r) for a large number of binary, ternary, and quaternary liquids in the equilibrium and supercooled (metastable liquid below the liquidus temperature) states. The data were obtained from x-ray scattering and volume measurements on levitated liquids using the electrostatic levitation technique. Although the volumes of all liquids expand with increasing temperature, the peak positions in g(r) for the first coordination shells contract for the majority of alloy liquids studied. The second and third peaks in g(r) expand, but at rates different from those expected from the volume expansion. This behavior is explained qualitatively in terms of changes in the coordination numbers and bond-lengths as clusters in liquids break up with increasing temperature.

Calculation of absorption and secondary scattering of X-rays by spherical amorphous materials in an asymmetric transmission geometry. Corrigendum.

A revised version of Table 2 of Bendert et al. [Acta Cryst. (2013). A69, 131-139] is provided.

Proposal for universality in the viscosity of metallic liquids.

The range of magnitude of the liquid viscosity, η, as a function of temperature is one of the most impressive of any physical property, changing by approximately 17 orders of magnitude from its extrapolated value at infinite temperature (ηo) to that at the glass transition temperature, Tg. We present experimental measurements of containerlessly processed metallic liquids that suggest that log(η/ηo) as a function of TA/T is a potentially universal scaled curve. In stark contrast to previous approaches, the scaling requires only two fitting parameters, which are on average predictable. The temperature TA corresponds to the onset of cooperative motion and is strongly correlated with Tg, suggesting that the processes underlying the glass transition first appear in the high temperature liquid.

Calculation of absorption and secondary scattering of X-rays by spherical amorphous materials in an asymmetric transmission geometry.

Expressions for absorption and the secondary scattering intensity ratio are presented for a small beam impinging off-center of a spherical amorphous sample. Large gradients in the absorption correction are observed from small offsets from the central axis. Additionally, the secondary scattering intensity ratio causes an intensity asymmetry in the detector image. The secondary scattering intensity ratio is presented in integral form and must be computed numerically. An analytic, small-angle, asymptotic series solution for the integral form of the absorption correction is also presented.