Real-time x-ray diffraction to examine elastic–plastic deformation in shocked lithium fluoride crystals

Abstract

Pressure effect and Mn doping in NaxCoO2 J. Appl. Phys. 112, 053503 (2012) Raman study of the Verwey transition in magnetite at high-pressure and low-temperature: Effect of Al doping J. Appl. Phys. 112, 043510 (2012) Dielectric spectroscopy and ultrasonic study of propylene carbonate under ultra-high pressures J. Chem. Phys. 137, 084502 (2012) Structural changes of filled ice Ic hydrogen hydrate under low temperatures and high pressures from 5 to 50 GPa J. Chem. Phys. 137, 074505 (2012) Additional information on Appl. Phys. Lett.

Ab initiomany-body Green's function calculations of optical properties of LiF at high pressures

“…We have predicted that the optical absorption spectrum should present dramatic P -dependent features well above the absorption edge, with both quasiparticle and optical gaps increas- ing with increasing hydrostatic stress. A marked increase in the magnitude of the near-edge absorption leads to the increase in the long-wavelength index of refraction with increasing P , as measured in numerous recent experiments 5,6,[8][9][10][11] . This trend compares well with DFT calculations which invoke an independent-particle picture 13 , even though the predicted absorption spectra in independent-particle vs. many-body pictures is so radically different.…”

“…After these objects have migrated to release the local strain, a final state is reached in which, on average, the material is hydrostatically (or isotropically) strained rather than uniaxially strained. The precise timescale for this relaxation of local deviatoric stresses is thought to be de- pendent upon the final stress as well as the stress history, and for LiF, our understanding is that these timescales have yet to be clearly established experimentally 6 . Anticipating that such transient regimes may eventually be measured, we present a few predictions for the optical properties of uniaxially-compressed LiF.…”

“…In such future studies of the solid, it will be important to consider the role of defects, dislocations, twinning, etc., some subset of which must necessarily be present when a hydrostatic state is reached by applying uniaxial strain beyond the elastic-plastic limit 6 . It is likely the case that these features, along with details of the liquid state, must be modeled accurately to obtain a comprehensive microscopic understanding of the detailed loss of transmission of LiF upon the application of suitably strong shocks 11 and ramps 10 .…”

“…DFT calculations of the optical properties of shocked LiF have been performed as well, some years before the recent study 13 , and in response to the interest in the refractive index from the experimental community 5,6 . In that work 15,16 , it was shown that DFT molecular dynamics predictions of the optical reflectivity are in reasonable agreement with experiment for the hot dense fluid (above ∼ 4.5 g/cm 3 for states on the principal Hugoniot).…”

“…Because of these applications (in addition to its fundamental interest as a prototypical wide-gap material) LiF itself has been the subject of a number of dynamic high-pressure experimental investigations [5][6][7][8][9][10][11] . Several of these have focused specifically on its high-pressure optical properties, and have collectively determined the real part of the index of refraction, n, for densities up to just over 4 g/cm 3 (∼ 60% increase in density above ambient) 5,[8][9][10][11] .…”