X-ray diffraction measurements to determine longitudinal and transverse lattice deformation in shocked LiF

Abstract

Experimental methods using both single and multiple x-ray diffraction were developed to determine real time, lattice deformation in directions parallel and perpendicular to shock wave propagation in single crystals subjected to plate impact loading. Initial experiments used single diffraction to monitor the interplanar spacing change, parallel to the shock propagation direction, in LiF crystals shocked along the [111] and [100] directions. These measurements, in combination with the macroscopic volume compression, were used to determine the state of compression of the unit cell. Subsequent development of a multiple diffraction technique permitted simultaneous determination of both the longitudinal and transverse lattice deformations. The present results showed that shock compression, below 4 GPa, along the [111] orientation—which results in macroscopic elastic deformation—produced one-dimensional unit cell compression. In contrast, shock compression along the [100] orientation—which results in macroscopic elastic-plastic deformation—produced isotropic unit cell compression. The implications of the present results and the ability to make quantitative x-ray diffraction measurements under shock loading are discussed.