Dynamic Compression of Solids

Academics

Justin Wark
Andy Higginbotham
Nigel Park
Andrew Comley

The long held belief that matter at multi-megabar pressures becomes simple, with close packed structures and metallic bonding prevailing across all materials, is increasingly under threat. Static techniques have found a range of unusual and unexpected structures at high pressure in even the simplest of elements. In addition, modern genetic structure search algorithms are finding that these complex structures appear to be stable across a host of materials, suggesting that far from being predictable, the high pressure regime may hold a host of surprises.

We employ high power lasers to transiently create matter at high pressures and density, while keeping temperatures sufficiently low to remain in the solid state. In particular, we are interested in interrogating the crystal structure, and the microstructure, using nanosecond, or even femtosecond pulses of x-rays. These x-rays are allowed to diffract from the sample, and through employing a range of diffraction geometries pioneered by the Oxford High Power Laser Group and collaborators, a range of material properties can be ascertained. Although these x-rays are traditionally from laser plasma sources, more recent work has begun to exploit the remarkable characteristics of X-ray Free Electron Lasers (XFELs).

More detailed discussion of the laser compression of condensed matter, and nano/femtosecond x-ray diffraction as a diagnostic, can be found here.