First-Principles Calculations of Electron-Phonon Interaction in Solid Materials: full-potential vs pseudopotential method

The calculations of electron-phonon (e-ph) interactions in solid materials from first-principles remain as an important fundamental and applied problem in condensed matter physics. The pseudopotential method has been successfully used to study the valence electronic structure and related physical properties of solid materials. However, when atoms move, they will carry their true electronic potentials with them, not pseudopotentials. The derivatives of true electronic potentials with respect to atomic shifts in a solid will be quite different from the derivatives of pseudopotentials with respect to the same atomic shifts because of the smooth and non-local nature of the pseudopotentials. The essential part of the calculations of e-ph interactions is a reliable computation of the derivatives of electronic potential with respect to atomic position shifts. Consequently, determining how to calculate e-ph interactions reliably by using a pseudopotential method remains as an open question for further research. Before the problems are solved, a full-potential method for the calculation of e-ph interactions can be used to circumvent the problems.