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

Abstract

Accurately modeling dense plasmas over wide ranging conditions of pressures and temperatures is a grand challenge critically important to our understanding of stellar and planetary physics as well as inertial confinement fusion. In this work, we investigate the thermodynamic, structural, and transport properties of carbon at warm and hot dense matter conditions using ab initio electronic structure methods. In particular, using the spectral quadrature (SQ) method, we report the first such results at the level of Kohn-Sham density functional theory; free of average-atom and/or orbital-free approximations. We carry out ab initio molecular dynamics simulations to calculate the equation of state (EOS), Hugoniot, pair distribution functions, and diffusion coefficients for carbon at densities between 8 g/cm 3 and 16 g/cm 3 and temperatures ranging from 100 kK to 10 MK. We find that the computed EOS and Hugoniot are in good agreement with the SESAME database and path integral Monte Carlo results. Additionally, we demonstrate the calculation of the ion-ion structure factor and viscosity for selected points that benefit from the linear and parallel scaling of the SQ method.

First-principles equation of state of CHON resin for inertial confinement fusion applications

“…The all-electron PIMC Hugoniot for CH has been widely acknowledged to be accurate and shown to be consistent with experiments [11][12][13][14]51,52]. If a similar relation between PIMC and OF-DFT-MD predictions of the compression maxima of CH is expected for CHON, deducted by a 1.4% increase due to the use of LKTγ TF (for CHON) rather than TF (for CH) functional (according to our tests), we estimate the real compression maximum of CHON to be ∼4.7 and occur at 50 TPa and 2 × 10 6 K. This can be veried by alternative methods, such as PIMC [48], spectral quadrature [53][54][55][56], extended DFT [51,[57][58][59] or hybrid Kohn-Sham+Thomas-Fermi [60], that improve the description of core electrons at such high temperatures, and tested in future experiments on gigabar (Gbar) platforms such as the National Ignition Facility [14].…”

Accurate Approximations of Density Functional Theory for Large Systems with Applications to Defects in Crystalline Solids

“…Therefore, the cubic scaling bottleneck inherent to traditional diagonalization approaches can be overcome using the SQ method, enabling the study of large system sizes that were previously intractable. Note that the unlike orbital-based diagonalization and linear scaling approaches, the cost of the SQ method decreases with increasing temperature [66,75], making it ideal for the study of materials under extreme conditions [93,90,7].…”