Mapping Cation Disorder in Copper Zinc Tin Sulfide via Atomic-Resolution Electron Energy-Loss Spectroscopy
Tong Cao1, Jinpeng Zhang1, Song Zuo1
1Institute of Advanced Interdisciplinary Studies & School of Chemistry and Chemical Engineering, Chongqing University, Chongqing, People's Republic of China.
Abstract:
Disorder in multinary crystals is often the hidden degree of freedom that governs phase stability, interfacial bonding, and functional performance. Here we establish an electron-crystallographic strategy that converts atomic-resolution electron energy-loss spectroscopy (AR-EELS) acquired along multiple zone axes into quantitative, site-specific occupancies, enabling 3D decoding of cation disorder in complex solids. Applying this approach to polytypic Cu-Zn-Sn-S (CZTS) nanocrystals, we directly resolve the cation sublattices in both zincblende- and wurtzite-derived polymorphs. We find reproducible Cu/Zn mixed occupancy without detectable site preference in both phases, whereas Sn remains fully ordered in the zincblende-derived polymorph but is partially replaced by Zn (∼35%) in the wurtzite-derived counterpart, consistent with its Zn-rich/Sn-poor composition. These experimentally constrained occupancies, together with reciprocal-lattice reconstruction, support average structural models consistent with I-42m and Pmn21 symmetry. Density functional theory further compares the energetics of candidate ordered and disordered structures at fixed compositions and supports the energetic plausibility of the experimentally constrained models. This AR-EELS electron-crystallography workflow provides a potentially transferable framework for occupancy-resolved analysis of multinary materials under suitable experimental and crystallographic conditions.
Related Concept Videos
02:58Crystal Field Theory - Octahedral Complexes
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
03:02Colors and Magnetism
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...