Demonstration of X-ray Thomson scattering as diagnostics for miscibility in warm dense matter

Abstract

The gas and ice giants in our solar system can be seen as a natural laboratory for the physics of highly compressed matter at temperatures up to thousands of kelvins. In turn, our understanding of their structure and evolution depends critically on our ability to model such matter. One key aspect is the miscibility of the elements in their interiors. Here, we demonstrate the feasibility of X-ray Thomson scattering to quantify the degree of species separation in a 1:1 carbon-hydrogen mixture at a pressure of~150 GPa and a temperature of 5000 K. Our measurements provide absolute values of the structure factor that encodes the microscopic arrangement of the particles. From these data, we find a lower limit of 24 þ6 À7 % of the carbon atoms forming isolated carbon clusters. In principle, this procedure can be employed for investigating the miscibility behaviour of any binary mixture at the highpressure environment of planetary interiors, in particular, for non-crystalline samples where it is difficult to obtain conclusive results from X-ray diffraction. Moreover, this method will enable unprecedented measurements of mixing/demixing kinetics in dense plasma environments, e.g., induced by chemistry or hydrodynamic instabilities.

Like dissolves like: A first-principles theory for predicting liquid miscibility and mixture dielectric constant

“…Liquid miscibility is a central consideration in many fields of science and technology, including separation/extraction ( 20 , 21 ), advanced materials formulation ( 22 , 23 ), food ( 24 ) and pharmaceutical ( 25 , 26 ) formulations, environment and sustainability ( 27 , 28 ), and even outer-space planet formation ( 29 ). Often, multicomponent mixtures are involved.…”

Properties of carbon up to 10 million kelvin from Kohn-Sham density functional theory molecular dynamics

“…The 8000 atom calculation agrees well with the predictions based on smaller cell sizes, but one significant advantage becomes evident: we can reach very small k values that extrapolate nicely to the compressibility limit S ii (k = 0) = k B T κ T , where k B is the Boltzmann constant and κ T is the compressibility. This is of crucial importance for X-ray Thomson scattering experiments [53][54][55] and the measurement of ion acoustic modes [52].…”

Nonequilibrium band occupation and optical response of gold after ultrafast XUV excitation

“…Theoretical models are needed here in two different ways: they provide estimates for the properties of highly excited matter that is created, and they also support the diagnostics by linking the microscopic states to the global behaviour measured. Interpreting transmission or reflectivity data 9 – 12 , X-ray or electron diffraction patterns 13 – 15 , or spectra from X-ray Thomson scattering 16 – 18 and X-ray near-edge spectroscopy 19 , 20 are examples where such models are required, in particular, for nonequilibrium conditions.…”