Ab initio study on anisotropic thermoelectric transport in ternary pnictide KZnP

Abstract

Strongly anisotropic bands near the Fermi level via band structure engineering have been proposed to enhance thermoelectric performance in functional materials. Recent works exhibit the presence of flat-and-dispersive-band-like strong anisotropy in a class of ternary transition metal pnictides. Taking KZnP as a representative example, here we investigate the thermoelectric properties of this class of materials based on first-principles calculations and semiclassical Boltzmann transport theory. Strikingly, the calculated lattice thermal conductivity k L shows a strong anisotropy with a small value of about 5.24 (2.58) W m −1 K −1 along the in-plane (out-of-plane) lattice direction at room temperature. Based on the electron relaxation time calculated from intensive ab initio electronphonon interactions, a thermoelectric figure of merit zT of 0.32 is predicted for n-type doped KZnP, about two times lower than the value estimated by the constant relaxation time approximation from deformation potential theory. Nanostructures with the characteristic length shorter than 13 nm can reduce the k L by 40%, enhancing zT to 0.52 along the c axis direction. This work supports that KZnP is a potential candidate for thermoelectric applications.

High-Throughput Screening of Rattling-Induced Ultralow Lattice Thermal Conductivity in Semiconductors

“…Yan et al predicted κ L values of 45 compounds, and the error compared with experimental values remained within 1 order of magnitude. More importantly, the results show that κ L value is more possible to be overestimated using the empirical equation in the range of low κ L values. , Figure demonstrates the κ L values calculated by the empirical equation as a function of the accurate κ L reported in the literature at 300 K, − which also proves this finding. In this work, structural information and general properties of all materials come from Materials Project Database, , including M̅ , V , n , d , and B .…”

“…Lattice thermal conductivities calculated by the empirical equation as a function of the accurate lattice thermal conductivities reported in the literature at 300 K. − …”

Theoretical insights into the structural, electronic and thermoelectric properties of the inorganic biphenylene monolayer

“…83 As τ is anisotropic and carrier dependent, the absolute values of electronic transport coefficients have been calculated using the mean value of τ (149.21–150 fs) calculated at room temperature. In similar 2D materials, the values of τ have been reported in the same order of 10 −13 s. 84–87…”

“…83 As t is anisotropic and carrier dependent, the absolute values of electronic transport coefficients have been calculated using the mean value of t (149.21-150 fs) calculated at room temperature. In similar 2D materials, the values of t have been reported in the same order of 10 À13 s. [84][85][86][87] Further, the t value at various temperatures has been estimated by the relation t T ¼ 300 Â t 300 T , where t T is the relaxation time at temperature T. 88,89 This relation could also be verified by using eqn (11).…”

Theoretical Investigation of the Lattice Thermal Conductivities of II–IV–V2 Pnictide Semiconductors

“…One of the most accurate approaches relies on solving the Boltzmann’s transport equation (BTE) for phonons, which requires calculating second- and third-order interatomic force constants (IFCs). Conventionally, these IFCs are determined by computing atomic forces in supercells for each symmetrically distinct displacement of atomic positions using density functional theory (DFT). ,,− However, obtaining third-order IFCs in this way requires a considerable number of DFT calculations, making this step a bottleneck in the first-principle prediction of κ. ,,,− Recently, innovative algorithms have emerged that expedite the calculation of IFCs by leveraging machine learning and related techniques to enable the extraction of IFCs from a much smaller set of DFT calculations. − These advancements pave the way for the accurate calculation of κ across a wide range of compositions, as we have shown before for chalcopyrite chalcogenides − and will demonstrate here for the chalcopyrite pnictides.…”