Phase stability of three-dimensional bulk and two-dimensional monolayer As1−xSbx solid solutions from first principles

A Ektarawong,B Alling,Y P Feng

doi:10.1088/1361-648x/ab0fd2

A Ektarawong, B Alling + Show 1 more

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https://doi.org/10.1088/1361-648x/ab0fd2

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Abstract

The mixing thermodynamics of both three-dimensional bulk and two-dimensional mono-layered alloys of As1−xSbx as a function of alloy composition and temperature are explored using a first-principles cluster-expansion method, combined with canonical Monte-Carlo simulations. We observe that, for the bulk phase, As1−xSbx alloy can exhibit not only chemical ordering of As and Sb atoms at x = 0.5 to form an ordered compound of AsSb stable upon annealing up to K, but also a miscibility gap at 475 K T 550 K in which two disordered solid solutions of As1−xSbx of different alloy compositions thermodynamically coexist. At T > 550 K, a single-phase solid solution of bulk As1−xSbx is predicted to be stable across the entire composition range. These results clearly explain the existing uncertainties in the alloying behavior of bulk As1−xSbx alloy, as previously reported in the literature, and also found to be in qualitative and quantitative agreement with the experimental observations. Interestingly, the alloying behavior of As1−xSbx is considerably altered, as the dimensionality of the material reduces from the three-dimensional bulk state to the two-dimensional mono-layered state—for example, a single-phase solid solution of monolayer As1−xSbx is predicted to be stable over the whole composition range at T > 250 K. This distinctly highlights an influence of the reduced dimensionality on the alloying behavior of As1−xSbx.

Highlights

We establish a database of different atomic configurations σ by using an algorithm developed by Hart and Forcade [36] to generate a set of 6104 configurations of bulk As1−xSbx alloy with up to 12 atoms in the primitive supercell, which is equivalent to six primitive rhombohedral unit cells
We demonstrate that As1−xSbx alloy forms a continuous series of disordered solid solutions over the whole composition range at T > 550 K, while at lower temperature we observe the existence of both the ordered compound of AsSb at x = 0.5 and clustering of As1−xSbx alloys of different compositions x
A miscibility gap is predicted to exist within a narrow temper ature range from ∼475 K to ∼550 K, in which bulk As1−xSbx alloy is thermodynamically stable as a mixture of As-rich and Sb-rich As1−xSbx solid solutions

Summary

Introduction

When speaking of the alloy, one should, be aware of the fact that in reality the constituent elements of the alloy can at a given temperature and alloy composition display different alloying behaviors, i.e. an ordering tendency to form an ordered structure, a clustering tendency toward phase segregation, and a mixing tendency to form a homogeneous solid solution. Those alloying behaviors are governed by the mixing thermodynamics of the alloy constituents, and to a large extent can affect the alloys properties

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