Functional Indium Vacancies in Indium Phosphors Chalcogenides

Layered Indium phosphorus trichalcogenides (In 4/3 P 2 X 6 ) have received significant attention due to their ordered indium vacancies and stacking-dependent properties, enabling applications in electronics, catalysis, and energy storage. However, the vacancy-governed stacking polytypes and atomic structures in In 4/3 P 2 X 6 remain elusive. Moreover, the facile reconstruction of the indium vacancies upon external stimulus makes their direct visualization challenging. Here, a low-dose aberration-corrected scanning transmission electron microscopy (STEM), four-dimensional STEM (4D-STEM) techniques, and density functional theory (DFT) are employed to systematically explore the atomic structure of In 4/3 P 2 X 6 and the magnetic properties of doped In 4/3 P 2 X 6 . The indium vacancies with glide-reflection symmetric ordering in In 4/3 P 2 X 6 are resolved at the atomic scale, driving armchair-type interlayer gliding with an unconventional step in In 4/3 P 2 Se 6 and zigzag-type gliding in In 4/3 P 2 S 6 , yielding ABC and nearly-ABC stacking polytypes, respectively. DFT calculations reveal that both gliding modes are energetically favorable, with their distinctions arising from the ligand-modulated interlayer charge distributions. Besides, filling the indium vacancies with magnetic dopants induces tunable magnetic ordering in In 4/3 P 2 X 6 , and also drives a structural transition to an MPX 3 -like phase and a non-magnetic paramagnetic (PM)−FM transition. This study sheds light on vacancy-governed structure in In 4/3 P 2 X 6 and highlights it as an excellent matrix for designing novel functional 2D magnets via doping engineering.