Convergence and pitfalls of density functional perturbation theory phonons calculations from a high-throughput perspective

Abstract

The diffusion of large databases collecting different kind of material properties from highthroughput density functional theory calculations has opened new paths in the study of materials science thanks to data mining and machine learning techniques. Phonon calculations have already been employed successfully to predict materials properties and interpret experimental data, e.g. phase stability, ferroelectricity and Raman spectra, so their availability for a large set of materials will further increase the analytical and predictive power at hand. Moving to a larger scale with density functional perturbation calculations, however, requires the presence of a robust framework to handle this challenging task. In light of this, we automatized the phonon calculation and applied the result to the analysis of the convergence trends for several materials. This allowed to identify and tackle some common problems emerging in this kind of simulations and to lay out the basis to obtain reliable phonon band structures from high-throughput calculations, as well as optimizing the approach to standard phonon simulations.

High-throughput density-functional perturbation theory phonons for inorganic materials

“…We have also observed 26 that the presence of small negative frequencies for the acoustic phonon frequencies in the close proximity of the Γ point could be associated with poor choices of the k or q point grids. In particular, we have observed that these are hardly ever a signal of a real incommensurate instability.…”

“…The Brillouin zone has been sampled using equivalent k -point and q -point grids that respect the symmetries of the crystal and with a density of approximately 1500 points per reciprocal atom, as suggested in ref. 26 . The q -point grid is always Γ-centered.…”

“… 25 ). In the present work, we report the full phonon band structures and derived quantities for 1521 semiconducting inorganic crystals, obtained following the procedure and the approximations detailed in our previous work 26 . The phonons are related to the second order derivatives of the energies with respect to the atomic displacements.…”

“…The methodology used in this work and the choice of the sampling of the Brillouin zone have been analyzed in a previous study 26 . There, it has been shown that properly converged results can be obtained with a sampling of the Brillouin zone that respects the symmetry of the system and with a density of 1500 points per reciprocal atom, both for the k -point and q -point sampling.…”

An Unlikely Route to Low Lattice Thermal Conductivity: Small Atoms in a Simple Layered Structure

“…The exchange-correlation functional was described using the PBEsol [42] approximation, that has proven to provide accurate phonon frequencies compared to experimental data [19]. Norm-conserving pseudopotentials [17] extracted from the Pseudodojo pseudopotentials table version 0.3 [61] were used for all the elements and the Brillouin zone was sampled with 8 × 8 × 5 Monkhorst-Pack grids [35], [43]. Due to standard DFT's known limitations in describing the band gap, we limit our analysis to Mg 3 Sb 2 , CaMg 2 Sb 2 and CaMg 2 Bi 2 , Fig.…”