Defect-free and crystallinity-preserving ductile deformation in semiconducting Ag2S

Abstract

Typical ductile materials are metals, which deform by the motion of defects like dislocations in association with non-directional metallic bonds. Unfortunately, this textbook mechanism does not operate in most inorganic semiconductors at ambient temperature, thus severely limiting the development of much-needed flexible electronic devices. We found a shear-deformation mechanism in a recently discovered ductile semiconductor, monoclinic-silver sulfide (Ag2S), which is defect-free, omni-directional, and preserving perfect crystallinity. Our first-principles molecular dynamics simulations elucidate the ductile deformation mechanism in monoclinic-Ag2S under six types of shear systems. Planer mass movement of sulfur atoms plays an important role for the remarkable structural recovery of sulfur-sublattice. This in turn arises from a distinctively high symmetry of the anion-sublattice in Ag2S, which is not seen in other brittle silver chalcogenides. Such mechanistic and lattice-symmetric understanding provides a guideline for designing even higher-performance ductile inorganic semiconductors.

Atomic perspective on plasticity mechanism of ionic-covalent systems from machine learning molecular dynamics simulations

“…The disordered structures can be identified by melt-quenching that allows detailed studies of the structural alterations corresponding to various points on the stress-strain curve. Before high-temperature treatment, the radial distribution function (RDF) peaks of S atoms are consistent with the calculations of Misawa et al 14 (Fig. 5a).…”

“…Since the extraordinary plasticity of α-Ag2S was experimentally revealed, the theoretical interpretations of its deformation mechanism have mainly relied on first-principles calculations. Low slip energy and high cleavage energy 1 , the excellent deformation capability of the Ag-S octahedral framework 13 , and the fracture-recombination of bonds 1,14 are considered to be evidence of plasticity. These studies have primarily explained the rationality of plastic deformation from energy, structure, and bonding, which have deepened our atomic-level understanding of the plasticity mechanisms in α-Ag2S, and also provided theoretical basis for the prediction and screening of other novel ductile and deformable semiconductors 15 .…”