Stability and Electronic Properties of K‐Sb and Na‐Sb Binary Crystals from High‐Throughput Ab Initio Calculations

Abstract

The study of the fundamental properties of alkali antimonide photocathodes for particle accelerators is currently hindered by the limited purity of the samples. First‐principles studies can effectively complement experiments to gain insight into the stability and the electronic structure of these compounds. In this high‐throughput analysis based on density‐functional theory (DFT), two families of binary crystals with K‐Sb and Na‐Sb compositions expected to form during evaporation of multi‐alkali antimonide photocathodes are investigated. Starting from an initial pool of structures mined from existing computational databases, automatized routines included in the in‐house developed library aim2dat are employed to determine the stability and the electronic properties of the aforementioned systems. By analyzing the formation energy, the structures are ranked in a convex hull retaining the information of their crystalline arrangement. Next, the band structure and the projected density of states of selected stable compounds are analyzed. Adopting the r2SCAN functional for the DFT calculations, reliable estimates of the character and size of the bandgaps are obtained and discussed in relation to the relative alkali content in the crystals. These results provide useful indications to predict and characterize binary phases forming during the growth of multi‐alkali antimonide photocathodes.