Ternary mixed-anion semiconductors with tunable band gaps from machine-learning and crystal structure prediction

Abstract

We report the computational investigation of a series of ternary X4Y2Z and X5Y2Z2 compounds with X={Mg, Ca, Sr, Ba}, Y={P, As, Sb, Bi}, and Z={S, Se, Te}. The compositions for these materials were predicted through a search guided by machine learning, while the structures were resolved using the minima hopping crystal structure prediction method. Based on ab initio calculations, we predict that many of these compounds are thermodynamically stable. In particular, 21 of the X4Y2Z compounds crystallize in a tetragonal structure with I-42d symmetry, and exhibit band gaps in the range of 0.3 and 1.8 eV, well suited for various energy applications. We show that several candidate compounds (in particular X4Y2Te and X4Sb2Se) exhibit good photo absorption in the visible range, while others (e.g., Ba4Sb2Se) show excellent thermoelectric performance due to a high power factor and extremely low lattice thermal conductivities.

A perspective on conventional high-temperature superconductors at high pressure: Methods and materials

“…It has been tested on a large set of materials classes [324,325], including superconducting hydrides at high pressure [159,326]. Although this package is not as popular as previously described algorithms, it is extremely powerful and reliable for large variety of situation and systems, including ternaries [327], Heusler-systems [328], etc. It is currently interfaced with a number of local structural optimization codes such as ABINIT, VASP, QE, GULP, SIESTA, LAMMPS, etc.…”

Ca4Sb2O and Ca4Bi2O: two promising mixed-anion thermoelectrics

“…25 However, systems which contain O 2 -and and another anion, for example BiCuOSe, show good p-type dopability and have emerged as promising p-type thermoelectrics. [26][27][28] In a recent computational study, 29 X 4 Y 2 Z mixed-anion compounds (X = Mg, Ca, Sr, Ba; Y = P, As, Sb, Bi; and Z = S, Se, Te) have been predicted to possess band gaps in the range suitable for many renewable-energy applications including as thermoelectrics. The study also revealed high band degeneracies, indicative of high power factors, and the complex crystal structures were found to yield low lattice thermal conductivities, with the room temperature κ l of Ba 4 Sb 2 Se being comparable to the flagship thermoelectric SnSe.…”

Bismuth-based mixed-anion compounds for anode materials in rechargeable batteries

“…Mixed-anion compounds are subject to an immense interdisciplinary interest compare to mono-anion compounds due to inheriting properties of different constituent anions in a single molecular material along with several new and interesting properties of additional orbital hybridization. [1][2][3] These properties can further be tuned by controlling the stoichiometry of the anions and charge rebalancing; thus, finding potential applications in a wide span including electrical, magnetic, optical, energy storage and transport devices. 1,4 Bismuth sulfide iodide system (Bi-S-I), a class of ternary mixed anion compounds possesses a quite complex phase diagram ranging of metastable/intermediate compositions, 5 along with thermodynamically stable phases of BiSI and Bi 19 S 27 I 3 .…”