Ab initio electronic transport and thermoelectric properties of solids from full and range-separated hybrid functionals

Abstract

Within the semiclassical Boltzmann transport theory in the constant relaxation-time approximation, we perform an ab initio study of the transport properties of selected systems, including crystalline solids and nanostructures. A local (Gaussian) basis set is adopted and exploited to analytically evaluate band velocities as well as to access full and range-separated hybrid functionals (such as B3LYP, PBE0, or HSE06) at a moderate computational cost. As a consequence of the analytical derivative, our approach is computationally efficient and does not suffer from problems related to band crossings. We investigate and compare the performance of a variety of hybrid functionals in evaluating Boltzmann conductivity. Demonstrative examples include silicon and aluminum bulk crystals as well as two thermoelectric materials (CoSb, BiTe). We observe that hybrid functionals other than providing more realistic bandgaps-as expected-lead to larger bandwidths and hence allow for a better estimate of transport properties, also in metallic systems. As a nanostructure prototype, we also investigate conductivity in boron-nitride (BN) substituted graphene, in which nanoribbons (nanoroads) alternate with BN ones.

Quantum‐mechanical condensed matter simulations with CRYSTAL

“…In a frozen band approximation, this information can be also correlated to the conductivity of the material at a given doping level (i.e., assuming that in the material permanently contains a number of carriers having energy in the conduction band). Our results in Figure and those in Sansone, Ferretti, and Maschio () can be directly compared to those obtained by other approaches (Madsen & Singh, ; Pizzi et al, ), showing excellent agreement despite the different basis set—that is a plane wave one in those cases.…”

“…In fact, approaches developed previously rely either on the interpolation of k-space eigenvalues (e.g., the BoltzTrap program, Madsen & Singh, 2006) or localization of the solution (e.g., the BoltzWann, Pizzi, Volja, Kozinsky, Fornari, & Marzari, 2014, program). We have recently implemented (Sansone, Ferretti, & Maschio, 2017) in Crystal a novel treatment for such derivatives that allows for an entirely analytical evaluation of band velocities. Thanks to the analytical differentiation, possible problems due to band crossings and/or numerical accuracy of the procedure are avoided.…”

Electronic, optical and thermoelectric properties of Fe2ZrP compound determined via first-principles calculations

“…Thus, to realize efficient energy conversion, a favorable thermoelectric material should possess high ZT, which indicates that a high Seebeck coefficient, high electrical conductivity, and low thermal conductivity are required for achieving efficient energy conversion. [5][6][7][8] In recent years, Heusler compounds have been theoretically investigated, and their TE properties have attracted signicant attention from researchers. [9][10][11][12][13][14][15][16][17] Generally, Heusler compounds have the stoichiometric composition XYZ or X 2 YZ and crystallize in the L2 1 structure, where X and Y are transition or rareearth metals and Z is the main group element.…”

Thermoelectric Properties of p-Type Cu2O, CuO, and NiO from Hybrid Density Functional Theory

“…We solve the transport coefficients of the materials both numerically using BoltzTraP and analytically using a novel method implemented in CRYSTAL17 by some of the present authors. 28,29 This allows us to provide a thorough comparison of the two computational strategies for both non-magnetic (Cu 2 O) and magnetic (CuO and NiO) materials.…”