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

TL;DR

This paper evaluates the pseudopotential approach in density-functional theory for atomic metallic hydrogen, comparing it with all-electron calculations, and examines its impact on phase stability, phonons, and superconductivity predictions.

Contribution

It provides a detailed comparison between pseudopotential and all-electron methods for atomic metallic hydrogen, highlighting differences in phase transition pressures and superconducting properties.

Findings

Pseudopotential and all-electron results agree on internal energies.

Significant differences in phase transition pressures and phonon spectral functions.

Superconducting T_c is higher in pseudopotential calculations for the first phase.

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.