First-principles study of structural stability, electronic properties and lattice thermal conductivity of KAgX (X = S, Se, Te)

Abstract

The present study is the first attempt towards establishing computational insights into the structural, electronic, mechanical, dynamical and thermal properties of the tetragonal phases of potassium chalcoargentates (KAgX). We find that the lattice thermal conductivity of KAgX is anisotropic, with values of 0.553 (0.279), 0.509 (0.369) and 0.221 (0.125) Wm −1 K −1 at room temperature (300 K) along the a-axis (c-axis) for KAgS, KAgSe and KAgTe, respectively. The calculated values of the lattice thermal conductivity are very small, especially along the c-axis. This highlights the potential of using KAgX in designing thermoelectric materials, since low lattice thermal conductivity is a requisite for maximizing the dimensionless figure of merit which defines the efficiency of a system in converting thermal to electrical energy and vice versa.

KAgX (X = S, Se): High-Performance Layered Thermoelectric Materials for Medium-Temperature Applications

“…Surprisingly, the κ l of KAgS and KAgSe monolayers are as low as 0.33 and 0.26 W m –1 K –1 at 300 K. Such low κ l are even comparable to those of the PbSe (0.26 W m –1 K –1 ) and δ-Cu 2 S monolayers (0.27 W m –1 K –1 ) . As indicated in Figure , we also find that the κ l of the KAgX monolayers are lower than the theoretical values of their bulk phase, reducing about 2 times. Hence, the KAgX monolayer is very likely to exhibit a good TE performance due to its ultralow κ l .…”

“…Calculated lattice thermal conductivity of the monolayer KAgX. For comparison, previous theoretical data for bulk are also presented.…”

Theoretical study of two-dimensional tetragonal transition metal chalcogenides and the potassium derivatives

“…[23][24][25][26] In addition, there are a number of studies on a series of ternary 2D layered transition metal chalcogenide compounds during recent years. [27][28][29][30] It is interesting to note in the above studies that the 2D KAgSe monolayer has a similar tetragonal structure to ZnSe and ZnS monolayers in our previous studies, and it could be considered that the potassium atoms cover the surfaces of the AgSe monolayer. The electronic and optical properties of ternary 2D layered transition metal chalcogenide compounds are different from their binary 2D layered transition metal chalcogenide counterparts.…”

“…Recently, rst-principles calculations were performed on the KAgSe monolayer due to its fascinating properties, [27][28][29][30] and the KAgSe monolayer structure is shown in Fig. 4a.…”

Ultralow lattice thermal conductivity and high thermoelectric performance of monolayer KCuTe: a first principles study

“…Furthermore, it also shows an ultralow κ l of 0.13 W m −1 K −1 at 300 K, which is lower than that of the KAgTe (0.22 W m −1 K −1 ). 47 Such low κ l indicates it might be possesses excellent TE response.…”