The use of the Rietveld method and pairs distribution function analysis to study the pressure dependence of the trigonal SnSe2 and SnS2 structure

TL;DR

This study uses Rietveld and pair distribution function analysis to investigate how high pressure affects the structure of trigonal SnSe2 and SnS2, revealing structural changes linked to improved thermoelectric properties.

Contribution

It applies combined Rietveld and pair distribution function methods to analyze pressure-induced structural changes in SnSe2 and SnS2, providing new insights into their pressure-dependent properties.

Findings

Interlayers distance X-X decreases faster than intralayer distance Sn-X under pressure.

Enhanced power factor observed at 20 GPa and 800 K for SnS2.

Structural changes correlate with thermoelectric performance improvements.

Abstract

A nanostructured trigonal SnSe2 was produced by mechanical alloying, and the effect of high-pressures up to 25.8 GPa on it was investigated. The literature reports refined structural data for SnS2 for pressures up to 20 GPa. These data were used as input data in a crystallographic software to calculate the shell structures around the Sn, Se, and S atoms placed at the origin. The shell structures were used to simulate the partial and total structure factors Sij(K) and S(K), and by Fourier transformation the partial and total pairs distribution functions Gij(R) and G(R) were obtained. The effect of high-pressure on the SnSe2 and SnS2 structures were followed by observing the changes in the Gij(R) functions. Also, the effect of high-pressure on the smallest angle Sn-X (X=Se,S)-Sn, intralayer distance Sn-X (X=Se,S), and interlayers distance X-X (X=Se,S) was studied. The interlayers distance X-X (X=Se,S) changes faster than the intralayer distance Sn-X (X=Se,S). An enhancement of the average power factor at 20 GPa and 800 K for SnS2 was reported. Using the interlayers distance S-S and intralayer distance Sn-S, it was evidenced that the enhancement of average power factor may be associated with the changes of the interlayers distance S-S that is faster than that of the intralayer distance Sn-S.