Contrasting Lone-Pair Stereochemistry in Sb 3+ and Bi 3+ Chalcogenides: Implications for Structure and Phonon Transport
Year: 2026
Type: article
Abstract: The unique physicochemical properties of chalcogenides containing post-transition metals are often governed by the stereochemical activity of their ns 2 lone pairs. A comparative structural analysis of bournonite (CuPbSbS 3 ) and aikinite (CuPbBiS 3 ) reveals that CuPbSbS 3 has a larger unit cell volume ( V = 552.58 Å 3 ) than CuPbBiS 3 ( V = 534.42 Å 3 ), despite antimony (Sb 3+ ) being smaller than bismuth (Bi 3+ ). This counterintuitive trend originates from the stronger lone pair effect of Sb 3+, which induces a larger static distortion, leading to a tetrahedral SbS 3 L ( l -lone pair) coordination, while Bi 3+ exhibits a less asymmetric distortion corresponding to the more compact square-pyramidal BiS 5 (or octahedral BiS 5 L) coordination. These structural differences are corroborated by temperature-dependent Raman spectroscopy, which captures distinct vibrational behaviors reflective of differing lattice dynamics. CuPbSbS 3 exhibits higher anharmonicity, as quantified by anharmonicity coefficients extracted from Raman data. Electron localization function analysis and crystal orbital Hamilton population further confirm the higher activity of the Sb 3+ lone pair compared to Bi 3+ . Interestingly, despite the lower atomic mass of Sb relative to Bi, both compounds exhibit nearly identical acoustic-phonon cutoff frequencies. Consequently, both CuPbSbS 3 and CuPbBiS 3 display partially suppressed Umklapp scattering and comparable low lattice thermal conductivities at high temperatures, despite their compositional and structural differences.
Source: Chemistry of Materials
Institutions: Centre National de la Recherche Scientifique, École Nationale Supérieure d'Ingénieurs de Caen, Laboratoire de Cristallographie et Sciences des Matériaux, Université de Caen Normandie, Institut Jean Lamour, Université de Lorraine, Chongqing University, Indian Institute of Technology Mandi, Institut des Sciences Chimiques de Rennes, Université de Rennes
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
Funder: Région Normandie
OpenAlex ID: W7154579749