Rigid muffin-tin approximation in plane-wave codes for fast modeling of phonon-mediated superconductors

Abstract We present a pseudopotential-based plane-wave implementation of the rigid muffin-tin approximation (RMTA), offering a computationally efficient alternative to its traditional use in all-electron codes. The RMTA partitions the total electron-phonon coupling constant into a sum of local atomic contributions, each defined as the product of electronic and ionic factors. The former is represented by McMillan–Hopfield parameters derived from angular-momentum-resolved electron-phonon matrix elements, while the latter can be obtained from the local force matrix. Here, we derive and incorporate the electronic part of the RMTA within the widely used pseudopotential framework. We show that the McMillan–Hopfield parameters for elemental transition metals and their compounds are in excellent agreement with the results of full-potential linearized augmented plane wave calculations. Furthermore, we formulate scalable strategies for computing the ionic factors and estimate the full electron-phonon coupling constant and critical temperature. Integration of RMTA descriptors into high-throughput workflows opens a cost-effective route for screening candidate superconductors.