Tuning the Sharing Modes and Composition in a Tetrahedral GeX 2 (X = S, Se) System via One-Dimensional Confinement.

The packing and connectivity of tetrahedral units are central themes in the structural and electronic properties of a host of solids. Here, we report one-dimensional (1D) chains of GeX 2 (X = S or Se) with modification of the tetrahedral connectivity at the single-chain limit. Precise tuning of the edge- and corner-sharing modes between GeX 2 blocks is achieved by diameter-dependent 1D confinement inside a carbon nanotube. Atomic-resolution scanning transmission electron microscopy directly confirms the existence of two distinct types of GeX 2 chains. Density functional theory calculations corroborate the diameter-dependent stability of the system and reveal an intriguing electronic structure that sensitively depends on tetrahedral connectivity and composition. GeS 2(1- x ) Se 2 x compound chains are also realized, which demonstrate the tunability of the system's semiconducting properties through composition engineering.