Band structure effects in x-ray scattering spectra of isochorically heated materials

X-ray Thomson scattering is a rich diagnostic commonly used to infer conditions of high energy density (HED) states. For example, applying the principle of detailed balance to ~10 eV plasmon shifts can be used to determine the electronic temperature. Meanwhile, angular dependence of the elastic scattering peak or detailed balance of ~100 meV Stokes and anti-Stokes lines constrains the ionic temperature. Using these techniques to measure both electronic and ionic temperatures of a nonequilibrium HED sample is challenging because of these states' short lifetimes and limited detector energy range and resolution. As a potential alternative, we predict subtle band structure effects at energy shifts of ~100 eV in the bound-free portion of the inelastic scattering spectrum of solid-density aluminum isochorically heated to 1 eV. Our real-time time-dependent density functional theory calculations show that these features vanish in melted aluminum and occur in a spectral range closer to the plasmon feature, perhaps enabling more efficient inference of both electronic and ionic temperature. These findings may advance studies of ultrafast melting or electron-ion coupling in materials out of thermodynamic equilibrium.