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Strongly-Coupled Coulomb Systems using finite-$T$ Density Functional Theory: A review of studies on Strongly-Coupled Coulomb Systems since the rise of DFT and SCCS-1977

The conferences on "Strongly Coupled Coulomb Systems" (SCCS) arose from the "Strongly Coupled Plasmas" meetings, inaugurated in 1977. The progress in SCCS theory is reviewed in an `author-centered' frame to limit its scope. Our efforts, i.e., with François Perrot, sought to apply density functional theory (DFT) to SCCS calculations. DFT was then poised to become the major computational scheme for condensed matter physics. The ion-sphere models of Salpeter and others evolved into useful average-atom models for finite-$T$ Coulomb systems, as in Lieberman's Inferno code. We replaced these by correlation-sphere models that exploit the description of matter via density functionals linked to pair-distributions. These methods provided practical computational means for studying strongly interacting electron-ion Coulomb systems like warm-dense matter (WDM). The staples of SCCS are wide-ranged, viz., equation of state, plasma spectroscopy, opacity (absorption, emission), scattering, level shifts, transport properties, e.g., electrical and heat conductivity, laser- and shock- created plasmas, their energy relaxation and transient properties etc. These calculations need pseudopotentials and exchange-correlation functionals applicable to finite-$T$ Coulomb systems that may be used in ab initio codes, molecular dynamics, etc. The search for simpler computational schemes has proceeded via proposals for orbital-free DFT, statistical potentials, classical maps of quantum systems using classical schemes like HNC to include strong coupling effects (CHNC). Laughlin's classical plasma map for the fractional quantum Hall effect (FQHE) is a seminal example where we report new results for graphene.