First-principles modeling of plasmons in aluminum under ambient and extreme conditions

Thermal excitation signals in the inhomogeneous warm dense electron gas

“…Similar to dielectric models, the electron-electron correlation is approximated in practice, but electron-ion collisions are tackled more directly. These calculations have become the workhorse among modern simulation methods in materials 54 , 55 and most recently also for WDM modeling 56 – 58 .…”

“…In prior diagnostics efforts of WDM, a homogeneous electronic structure of the samples has commonly been assumed, particularly regarding the modeling aspects. Under this assumption, the electronic temperature of the induced WDM states has been determined from X-Ray Thomson scattering signals, for instance, in warm dense aluminum either by dielectric models 59 or KS-DFT calculations 57 , 58 , 60 . Despite the combined efforts of experiment and simulation, determining the electronic temperature is still subject to significant uncertainties 61 .…”

Predictions of bound-bound transition signatures in x-ray Thomson scattering

“…By finding the model inputs (i.e., physical variables) that predict the DSF that best agrees with the measured scattering cross section, one can infer the values of the physical variables that produced the data. Broadly, models for the DSF can be separated into first-principles models that rely on approximating the inter-particle interaction (e.g., electronic exchange and correlation [16][17][18] or the absence of an attractive ionic potential [19,20]); singlecenter average-atom (AA) models [21,22]; and simplified models [7] that rely on approximations to less fundamental quantities (e.g. the average ion charge Z [23]).…”

“…the average ion charge Z [23]). While first-principles models have been used to assess sensitivities of the DSF to, e.g., temperature [17,18], the computational cost of these models is too great for rigorous inference and the intrinsic systematic errors aren't yet sufficiently well-characterized for them to serve as a ground truth. Nevertheless, these models provide a critical mooring post in a sea of uncertainties and can validate other approximations made by simpler, less expensive models [16].…”

Path Integral Monte Carlo Simulations of liquid $^3$He without Fixed Nodes: Structural Properties and Collective Excitations

“…5 for q = 1.62 Å−1 [top] and q = 2.01 Å−1 [bottom]. Such comparisons are of fundamental importance to assess the quality of a theoretical method, as the peak position contains comparably limited information [54]. Evidently, the two independent data sets are in excellent agreement over the entire frequency range.…”