Abstract
We present a new solid-state material phase which is a disordered solid solution but offers many ordered line-compound features. The emergent physical phenomena are rooted in the perfect short-range order which conserves the local octet rule. We model the dual-sublattice-mixed semiconductor alloy {mathrm{(ZnSnN}}_{mathrm{2}}{mathrm{)}}_{1 - x}{mathrm{(ZnO)}}_{2x} using first-principles calculations, Monte-Carlo simulations with a model Hamiltonian, and an extension of the regular solution model by incorporating short-range order. We demonstrate that this unique solid solution, occurring at a “magic” composition, can provide an electronically pristine character without disorder-induced charge localization and, therefore, a superior carrier transport similar to ordered phases. Interestingly, this phase shows singularities that are absent in the conventional solid-solution models, such as the regular solution and band-gap bowing model. Thermodynamically, this alloy phase has a sharply reduced enthalpy at its composition (like a line compound), but it still requires the entropy from long-range disorder to be stabilized at experimentally accessible temperatures.
Highlights
Materials properties depend on composition[1,2] and atomic arrangement[3,4]
Rather than atoms in binary alloys, the building blocks are formed by the local motif structures. This treatment separates the degrees of freedom into the short-range order (SRO) and long-range order (LRO, beyond the first shell) parts in the partition function as Z = ZSROZLRO
ZSRO depends on the internal degrees of freedom in the local structure and ZLRO relates to the arrangement of motifs
Summary
Materials properties depend on composition[1,2] and atomic arrangement[3,4]. Since the Bronze Age, solid solutions, formed by alloying elements to occupy interstitial or substitutional lattice sites of metal crystals, have been used to increase the mechanical strength. Properties of interest can be tuned by composition without changing the underlying lattice structure. The absence of translational symmetry in solid solutions causes charge localization which is adverse to carrier transport[16]. To solve this dilemma, in this paper, we report a discovery of a solid-state material phase that combines solid-solution and line-compound features. In this paper, we report a discovery of a solid-state material phase that combines solid-solution and line-compound features In this unique alloy phase, perfect short-range order restores properties that are otherwise typical of ordered phases, such as the absence of charge localization
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