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First-principles screening of materials with extreme effective masses

Szymon Błazucki, Junfeng Qiao, Nicola Marzari

Abstract

The effective mass of charge carriers is a fundamental descriptor of the electronic structure of materials, and can be used to assess performance in electronics applications, or to screen for thermoelectrics and transparent conductors. Here, we perform a high-throughput computational screening of approximately 20,000 experimentally known three-dimensional stoichiometric inorganics obtained from the Materials Cloud 3D structure database. By combining density-functional theory calculations and maximally localized Wannier functions, we are able to compute the full conductivity effective mass tensor for electrons and holes from the Boltzmann transport equation in the constant relaxation-time approximation. This approach captures the effects of band non-parabolicity, anisotropy, and valley multiplicity that would be neglected by standard parabolic fittings. The screening identifies a curated set of candidates exhibiting extreme electronic properties, from ultra-low to ultra-large effective masses, these latter associated with flat-band physics. We validate the workflow by recovering established high-mobility semiconductors and highlight promising novel candidates. Furthermore, we classify materials by their mass anisotropy and discuss the physical limits of defining a conductivity effective mass in narrow-gap regimes at room temperature. The resulting dataset provides a systematic roadmap to search for high-performance materials in novel chemical spaces.

First-principles screening of materials with extreme effective masses

Abstract

The effective mass of charge carriers is a fundamental descriptor of the electronic structure of materials, and can be used to assess performance in electronics applications, or to screen for thermoelectrics and transparent conductors. Here, we perform a high-throughput computational screening of approximately 20,000 experimentally known three-dimensional stoichiometric inorganics obtained from the Materials Cloud 3D structure database. By combining density-functional theory calculations and maximally localized Wannier functions, we are able to compute the full conductivity effective mass tensor for electrons and holes from the Boltzmann transport equation in the constant relaxation-time approximation. This approach captures the effects of band non-parabolicity, anisotropy, and valley multiplicity that would be neglected by standard parabolic fittings. The screening identifies a curated set of candidates exhibiting extreme electronic properties, from ultra-low to ultra-large effective masses, these latter associated with flat-band physics. We validate the workflow by recovering established high-mobility semiconductors and highlight promising novel candidates. Furthermore, we classify materials by their mass anisotropy and discuss the physical limits of defining a conductivity effective mass in narrow-gap regimes at room temperature. The resulting dataset provides a systematic roadmap to search for high-performance materials in novel chemical spaces.

Paper Structure

This paper contains 8 sections, 3 equations, 4 figures, 1 table.

Table of Contents

  1. Introduction
  2. Results
  3. Screening and Filtering Criteria
  4. Computation of Conductivity Effective Masses
  5. Effective mass distribution
  6. Discussion
  7. Candidate validation and dataset reliability
  8. Trends across the database

Figures (4)

  • Figure 1: Filtering process.
  • Figure 2: Scatter plot of effective mass against the bandgap at three different doping values in [$\text{cm}^{-3}$]
  • Figure 3: Effect of doping on effective mass. a) Calculated band structure for the GaLiSi, b) Corresponding density of states with Fermi-Dirac distribution centred at Fermi level at 0K and 300K. The red line is $n_{carrier}$ which is a product of density of states and Fermi distribution $f(T=300K)$ for holes at the valence band side, and electrons at the conduction band side. c) Calculated effective masses in principal directions for electrons and holes as a function of doping. d) Enlarged Valence Band Maximum (VBM) and Conduction Band Minimum (CBM) with shaded rectangles indicating range of Fermi Dirac functions where $10^{-3}<f(T=300K)<1-10^{-3}$.
  • Figure 4: Histogram of electron effective mass for top candidates at $10^{18}$ doping [cm$^{-3}$] (columns coloured by manual filtering result)