Disordered Systems Group

Universal Two-Component Dynamics in Supercritical Fluids

Despite the technological importance of supercritical fluids, controversy remains about the details of their microscopic dynamics. In this work, we study four supercritical fluid systems─water, Si, Te, and Lennard-Jones fluid─via classical molecular dynamics simulations. A universal two-component behavior is observed in the intermolecular dynamics of these systems, and the changing …

High-resolution inelastic x-ray scattering at the high energy density scientific instrument at the Free-Electron Laser

We introduce a setup to measure high-resolution inelastic x-ray scattering at the High Energy Density scientific instrument at the European X-Ray Free-Electron Laser (XFEL). The setup uses the Si (533) reflection in a channel-cut monochromator and three spherical diced analyzer crystals in near-backscattering geometry to reach a high spectral resolution. …

Experimental evidence of mosaic structure in strongly supercooled molecular liquids

When a liquid is cooled to produce a glass its dynamics, dominated by the structural relaxation, become very slow, and at the glass-transition temperature Tg its characteristic relaxation time is about 100 s. At slightly elevated temperatures (~1.2 Tg) however, a second process known as the Johari-Goldstein relaxation, βJG, decouples from the …

Microscopic pathways for stress relaxation in repulsive colloidal glasses

Residual stresses are well-known companions of all glassy materials. They affect and, in many cases, even strongly modify important material properties like the mechanical response and the optical transparency. The mechanisms through which stresses affect such properties are, in many cases, still under study, and their full understanding can pave …

Lithium Borates from the Glass to the Melt: A Temperature-Induced Structural Transformation Viewed from the Boron and Oxygen Atoms

A multiedge study of the local structure of lithium borate glasses and melts has been carried out using X-ray Raman scattering (XRS) as a function of temperature. Thanks to a wide range of compositions, from pure B2O3 up to the metaborate composition, we are able to finely interpret the modifications …