EXAFS studies of the local environment of lead and selenium atoms in PbTe$_{1-x}$Se$_x$ solid solution

TL;DR

This study uses EXAFS spectroscopy to analyze the local atomic environment in PbTe$_{1-x}$Se$_x$ solid solutions, revealing complex structural features influenced by chemical factors and deviations from ideal models.

Contribution

It provides detailed insights into the local structure and chemical influences in PbTe$_{1-x}$Se$_x$, including bond length distributions and the role of chemical factors in the enthalpy of mixing.

Findings

Bimodal distribution of bond lengths in the first shell

Large Debye--Waller factors for Pb--Pb distances in the second shell

Chemical factors significantly influence the structure and enthalpy of mixing

Abstract

EXAFS spectroscopy is used to study the local environment of lead and selenium atoms in PbTe$_{1-x}$Se$_x$ solid solution. In addition to a bimodal distribution of bond lengths in the first shell, unusually large Debye--Waller factors for the Pb--Pb interatomic distances in the second shell and a substantial deviation of these distances from Vegard's law are observed. Valence force field (VFF) calculations show that these observations are due to the complex structure of the distribution function for Pb--Pb distances. It is found that the number of Se--Se pairs in the second shell surpasses the statistical value, which indicates that chemical factors play an important role in the structure of the solid solution. The contribution of these chemical factors to the enthalpy of mixing of the solid is estimated to be approximately 0.5 kcal/mole, which is comparable to the strain contribution.