Abstract
Despite the fast development of computational materials modelling, theoretical description of macroscopic elastic properties of textured polycrystalline aggregates starting from basic principles remains a challenging task. In this communication we use a supercell-based approach to obtain the elastic properties of random solid solution cubic ZrAlN system as a function of the metallic sublattice composition and texture descriptors. The employed special quasi-random structures are optimised not only with respect to short range order parameters, but also to make the three cubic directions $[1\,0\,0]$, $[0\,1\,0]$, and $[0\,0\,1]$ as similar as possible. In this way, only a small spread of elastic constants tensor components is achieved and an optimum trade-off between modelling of chemical disorder and computational limits regarding the supercell size is achieved. The single crystal elastic constants are shown to vary smoothly with composition, yielding $x\approx0.4$-0.5 an alloy constitution with an almost isotropic response. Consequently, polycrystals with this composition are suggested to have Young's modulus independent on the actual microstructure. This is indeed confirmed by explicit calculations of polycrystal elastic properties, both within the isotropic aggregate limit, as well as with fibre textures with various orientations and sharpness. It turns out, that for low AlN mole fractions, the spread of the possible Young's moduli data caused by the texture variation can be larger than 100 GPa. Consequently, our discussion of Young's modulus data of cubic ZrAlN contains also the evaluation of the texture typical for thin films.
Highlights
Quantum mechanical calculations using density functional theory (DFT) of structural and elastic properties of materials have become a standard tool in modern computational material science
The alloying trends have been extensively investigated, which in the area of hard protective coatings addressed predominantly issues related to the phase stability. This has been possible due to the increased computational power and the development of theories for treating random solid solutions. These include effective potential methods [7], cluster methods [8,9], or supercell-based approaches, such as the special quasirandom structure (SQS) [10] technique employed in this paper
In this work we investigate a possible trade-off between the randomness and the overall effective symmetry by introducing directionally optimized SQSs (DOSQSs)
Summary
Quantum mechanical calculations using density functional theory (DFT) of structural and elastic properties of materials have become a standard tool in modern computational material science. [1,2,3,4,5,6]) This has been possible due to the increased computational power and the development of theories for treating random solid solutions. These include effective potential methods [7] (e.g., the coherent potential approximation or virtual coherent approximation), cluster methods [8,9] (e.g., the cluster expansion method), or supercell-based approaches, such as the special quasirandom structure (SQS) [10] technique employed in this paper.
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