The hitherto unexplored surface structural and dynamical properties of the thermoelectric material β-Cu₂S chalcocite, are uncovered using ab initio molecular dynamics simulations at 450 K. The material exhibits a hybrid crystalline-liquid behavior, with the liquidlike dynamics of the Cu atoms and the crystalline order of the sulfur sublattice. The topmost nanoscale region of the material is predicted to undergo significant structural relaxation, resulting in a ∼10% increase in the distance between the topmost S-layers accompanied by an increased Cu density. Cu diffusion in the interlayer regions of the surface S-sublattice is enhanced (doubled) compared to the bulk value, and an underlying microscopic mechanism, entailing marked emergent surface-induced softening of the S-sublattice vibrational dynamics, is described.

中文翻译：

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β-Cu2S辉铜矿表面的结构弛豫和液态Cu扩散增强

迄今为止尚未探索的热电材料 β-Cu _{2 的}表面结构和动力学特性S 辉铜矿是在 450 K 下使用 ab initio 分子动力学模拟发现的。该材料表现出混合结晶-液体行为，具有 Cu 原子的类液体动力学和硫亚晶格的结晶顺序。预计材料的最顶部纳米级区域将经历显着的结构松弛，导致最顶部 S 层之间的距离增加约 10%，同时铜密度增加。与体值相比，表面 S 亚晶格的层间区域中的铜扩散增强（加倍），并且描述了潜在的微观机制，导致 S 亚晶格振动动力学显着的表面诱导软化。