Investigation of the temperature in dense carbon near the solid-liquid phase transition between 100 GPa and 200 GPa with spectrally resolved X-ray scattering

Abstract

We present experiments investigating dense carbon at pressures between 100 GPa and 200 GPa and temperatures between 5,000 K and 15,000 K. High-pressure samples with different temperatures were created by laser-driven shock compression of graphite and varying the initial density from 1.53 g/cm3 to 2.21 g/cm3 and the drive laser intensity from 7.1 TW/cm2 to 14.2 TW/cm2. In order to deduce temperatures, spectrally resolved X-ray scattering was applied to determine ion-ion structure factors at a scattering vector of k = 4.12·1010m−1, which shows high sensitivity to temperature for the investigated sample conditions. After comparison to corresponding DFT-MD simulations, we were able to assign each structure factor a temperature. This information is indicative of the expected temperature range for the melting line of carbon at high pressures and can be compared to theoretical predictions.