Elastic and inelastic shock compression of diamond and other minerals

Laser-driven shock wave experiments have been used to examine the response of diamond and quartz to conditions of high dynamic stress, and finite-strain theory has been developed to treat the shock response of these and other high-strength minerals in the elastic shock-compression regime. For diamond, two-wave shock structures featuring an elastic-precursor shock followed by an inelastic shock are observed. The Hugoniot elastic limits of diamond are measured to be 80.1 (+/- 12.4), 80.7 (+/- 5.8) and 60.4 (+/- 3.3) GPa for <100>, <110> and <111> orientations, respectively. The elastic yield strength of diamond inferred from these measurements is 75 (+/- 20) GPa and is strongly anisotropic. Inelastic-compression states beyond the Hugoniot elastic limit show a varying degree of strength retention, with the <111> orientation showing a retention of strength and the <110> orientation showing a loss of strength, based on comparisons with the ideal hydrostatic shock response of diamond. Diamond is nontransparent to VISAR interferometry above its elastic limit, likely due to scattering of light in shocked diamond behind the inelastic wave. The elastic-precursor shock is transparent; for elastic-uniaxial strain in the <100> and <110> directions the index of refraction along the compression axis increases. The two-wave structure in diamond is expected to persist to at least 450 GPa and to even higher stresses for short-duration experiments; this is inconsistent with the commonly used Hugoniot of diamond reported by Pavlovskii (1971). For alpha-quartz, a transition from optically transparent to reflecting is identified at a pressure of ∼ 80 GPa on the Hugoniot. The VISAR index of refraction correction for transparent quartz at high pressure is found to be 1.16 (+/- 0.04). Eulerian and Lagrangian finite-strain formulations are developed to treat the case of elastic-shock compression at low stresses, for application to diamond, quartz and sapphire.