Confined ionic order in atomic nanowires of rare-earth chlorides unveiled via symmetry-guided structural screening.

Low-dimensional materials can exhibit unusual structural, electronic, and magnetic properties that arise from nanoscale confinement and quantum effects. However, determining their local atomic structures remains challenging, especially when long-range periodicity is limited and conventional crystallographic approaches are difficult to apply. Here, we show a symmetry-guided screening strategy for resolving confined one-dimensional materials by combining scanning transmission electron microscopy with reactive force-field molecular dynamics and density functional theory. We encapsulate rare-earth chlorides within single-walled carbon nanotubes (SWCNTs) to form stable LnCl3@SWCNTs hybrids (Ln = Y, Gd, Dy, Er), which contain ordered one-dimensional atomic nanowires. The screening strategy identifies structural models that are consistent with experimental imaging and energetic stability, enabling local configurations to be distinguished. Electronic and magnetic analyses, particularly for Dy-based systems using complete active space self-consistent field calculations and Boltzmann transport theory, reveal how local symmetry and confinement influence their functional properties. This experiment-theory framework provides a broadly applicable route for probing short-range-ordered nanostructures, establishing structure-property correlations, and guiding the design of functional low-dimensional materials.