Topologically close-packed phases in binary transition-metal compounds: matching high-throughput ab initio calculations to an empirical structure map

被引：39

作者：

Hammerschmidt, T. ^{[1
,2
]}

Bialon, A. F. ^{[1
]}

Pettifor, D. G. ^{[2
]}

Drautz, R. ^{[1
,2
]}

机构：

[1] Ruhr Univ Bochum, ICAMS, Bochum, Germany

[2] Univ Oxford, Dept Mat, Oxford OX1 3PH, England

来源：

NEW JOURNAL OF PHYSICS | 2013年 / 15卷

基金：

英国工程与自然科学研究理事会;

关键词：

TOTAL-ENERGY CALCULATIONS; ELECTRONIC-STRUCTURE; CRYSTAL-STRUCTURE; STABILITY; SYSTEMS;

D O I：

10.1088/1367-2630/15/11/115016

中图分类号：

O4 [物理学];

学科分类号：

0702 ;

摘要：

In steels and single-crystal superalloys the control of the formation of topologically close-packed (TCP) phases is critical for the performance of the material. The structural stability of TCP phases in multi-component transition-metal alloys may be rationalized in terms of the average valence-electron count (N) over bar and the composition-dependent relative volume-difference Delta(V) over bar / (V) over bar We elucidate the interplay of these factors by comparing density-functional theory calculations to an empirical structure map based on experimental data. In particular, we calculate the heat of formation for the TCP phases A15, C14, C15, C36, x, mu and sigma for all possible binary occupations of the Wyckoff positions. We discuss the isovalent systems V/Nb-Ta to highlight the role of atomic-size difference and observe the expected stabilization of C14/C15/C36/mu by Delta(V) over bar / (V) over bar at Delta N = 0 in V-Ta. In the systems V/Nb-Re, we focus on the well-known trend of A15 -> sigma -> x stability with increasing (N) over bar and show that the influence of Delta(V) over bar / (V) over bar is too weak to stabilize C14/C15/C36/mu in Nb-Re. As an example for a significant influence of both (N) over bar and Delta(V) over bar / (V) over bar, we also consider the systems Cr/Mo-Co. Here the sequence A15 ->sigma -> x is observed in both systems but in Mo-Co the large size-mismatch stabilizes C14/C15/C36/mu. We also include V/Nb-Co that cover the entire valence range of TCP stability and also show the stabilization of C14/C15/C36/mu. Moreover, the combination of a large volume-difference with a large mismatch in valence-electron count reduces the stability of the A15/sigma/x phases in Nb-Co as compared to V-Co. By comparison to nonmagnetic calculations we also find that magnetism is of minor importance for the structural stability of TCP phases in Cr/Mo-Co and in V/ Nb-Co.

引用

页数：18

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