8-electron Half-Heusler compounds as promising energy materials: A high throughput first principles study

 

Vikram, Bhawna Sahni, C.K. Barman and Aftab Alam

 

Department of Physics, Indian Institute of Technology, Powai, Mumbai 400 076, India

 

We present a high throughput study of I-III-IV class of Half Heusler (HH) alloys with 8 valence-electrons using first-principles calculations based on Density Functional Theory. The objective of our study is to find novel materials for three applications: - (i) thermoelectric (ii) topological insulators (TIs) and (iii) optoelectronic applications. HH alloys with 8-valence electrons are chosen for our study as they are not much explored. The screening parameters used for this study are formation energy, phonon dispersion, accurate band gaps using GW potentials, nature of bandgap, thermoelectric figure of merit and topological band inversion. Based on initial screening parameters, 21 compounds were shortlisted to study for thermoelectric (TE) properties. Out of these 21 compounds, 6 were found to have excellent TE performance (figure of merit ZT>0.8). 17 compounds were found to show robust topological insulating behaviour confirmed by bulk band inversion and surface conducting states. 2 compounds showed relatively large bandgap and can be promoted for possible optoelectronic applications via some band engineering. We strongly suggest experimental characterization of these promising candidates to shed more light on the present findings.

 

References:

 

[1] Graf T., Felser C. & Parkin S. S. P. Simple rules for the understanding of Heusler compounds. Prog. Solid State Chem. 39, 1-50 (2011).
[2] Romain Gautier, Xiuwen Zhang, et al. Prediction and accelerated laboratory discovery of previously unknown 18-electron ABX compounds. Nature Chemistry 7,308-316 (2015).