Electrical conductivity of warm dense silica from double-shock experiments

Abstract

Understanding materials behaviour under extreme thermodynamic conditions is fundamental in many branches of science, including High-Energy-Density physics, fusion research, material and planetary science. Silica (SiO2) is of primary importance as a key component of rocky planets’ mantles. Dynamic compression is the most promising approach to explore molten silicates under extreme conditions. Although most experimental studies are restricted to the Hugoniot curve, a wider range of conditions must be reached to distill temperature and pressure effects. Here we present direct measurements of equation of state and two-colour reflectivity of double-shocked α-quartz on a large ensemble of thermodynamic conditions, which were until now unexplored. Combining experimental reflectivity data with numerical simulations we determine the electrical conductivity. The latter is almost constant with pressure while highly dependent on temperature, which is consistent with simulations results. Based on our findings, we conclude that dynamo processes are likely in Super-Earths’ mantles.

Shock compression of coesite up to 950 GPa

“…Other symbols (star, asterisk, plus) and open symbols are from the previous experimental data and isothermal data by Density Functional Theory (DFT) data, respectively. [Guarguaglini et al, 2021;Hicks et al, 2006;Mazevet et al, 2015;Millot et al, 2015;Scipioni et al, 2017]. A range of interior condition for Jupiter is indicated by the dashed curves.…”

The advent of ab initio simulations of dense plasmas

“…But combining ab initio predictions with optical measurements offers the possibility to determine more accurate experimentally derived DC conductivity based on reflectivity measurements in the visible range. [ 66 ]…”

Impact of neutrals on the plasma screening length

“…2012; Guarguaglini et al. 2021). Despite recent progress in experimentation and computer simulation, WDM still poses significant problems from the viewpoint of theoretical understanding since it is a rather ambitious goal to simultaneously cope with a whole range of phenomena as dissimilar as quantum effects, well pronounced interparticle correlations, partial ionization, electron degeneracy, etc.…”

“…atoms and molecules, must be somehow incorporated into the scrutiny. This is especially true for astrophysical applications such as the interiors of giant planets, white and brown dwarfs (Chabrier et al 2000;Knudson et al 2012;Soubiran et al 2017) as well as for shock-compression experiments (Hamel et al 2012;Guarguaglini et al 2021). Despite recent progress in experimentation and computer simulation, WDM still poses significant problems from the viewpoint of theoretical understanding since it is a rather ambitious goal to simultaneously cope with a whole range of phenomena as dissimilar as quantum effects, well pronounced interparticle correlations, partial ionization, electron degeneracy, etc.…”