The pseudopotential approach within density-functional theory: the case of atomic metallic hydrogen

Abstract

Internal energies, enthalpies, phonon dispersion curves, and superconductivity of atomic metallic hydrogen are calculated. The (standard) use pseudopotentials in density-functional theory are compared with full (Coulomb)-potential all-electron linear muffin-tin orbital calculations. Quantitatively similar results are found as far as internal energies are concerned. Larger differences are found for phase-transition pressures; significant enough to affect the phase diagram. Electron--phonon spectral functions ${\alpha }^{2}F(\omega )$ also show significant differences. Against expectation, the estimated superconducting critical temperature T${}_c$ of the first atomic metallic phase I4${}_1$/amd (Cs-IV) at $500$ GPa is actually higher.