Carrier-selective dimensional crossover from bulk stibnite Sb2S3 to the single-chain limit

Low-dimensional materials display physical properties markedly different from their bulk counterparts because of quantum confinement. Chain-based chalcogenides provide pre-formed structural motifs for exploring one-dimensional (1D) electronic behaviour without cutting or passivating an extended two-dimensional lattice. In the present work, we use hybrid density functional calculations and semiclassical Boltzmann transport theory to characterize the mineral stibnite (Sb 2 S 3 ) across its structural hierarchy, from the bulk (3D) crystal to the natural (100) cleavage layer (2D) and finally to the unsupported single-chain limit. Phonon dispersions show that both 2D and 1D models are dynamically stable, while the energy analysis quantifies the progressive removal of inter-chain interactions. The 2D layer retains a slightly enlarged indirect gap and exhibits the most dispersive chain-direction conduction band, giving the lightest electron mass among the three systems. By contrast, complete chain isolation opens a wider direct gap and produces an exceptionally flat, strongly non-parabolic valence-band edge together with finite full-zone dispersion. Transport calculations at equal carrier loading reveal a carrier-polarity-dependent crossover: hole transport evolves comparatively regularly from bulk to layer to chain, whereas the electron branch is non-monotonic because the highly dispersive 2D conduction band combines high conductivity with weak energy selectivity. Water adsorption weakly perturbs the isolated chain, while oxygen produces structural activation and an in-gap hybrid state. These results define the intrinsic single-chain reference for Sb 2 S 3 and clarify how partial and complete inter-chain decoupling reorganize its frontier electronic states.