Theoretical study of ordering in Fe-Al alloys based an a density-functional generalized-perturbation method

被引:34
作者
Bose, SK
Drchal, V
Kudrnovsky, J
Jepsen, O
Andersen, OK
机构
[1] MAX PLANCK INST FESTKORPERFORSCH, D-70569 STUTTGART, GERMANY
[2] BROCK UNIV, DEPT PHYS, ST CATHARINES, ON L2S 3A1, CANADA
[3] ACAD SCI CZECH REPUBL, INST PHYS, CZ-18040 PRAGUE, CZECH REPUBLIC
[4] VIENNA TECH UNIV, INST TECH ELECTROCHEM, A-1060 VIENNA, AUSTRIA
关键词
D O I
10.1103/PhysRevB.55.8184
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
We present a theoretical study of ordering in Fe-Al alloys assuming different underlying magnetic structures: paramagnetic, ferromagnetic, and disordered local moments (DLM's). We calculate the effective pair (chemical) interactions using the generalized perturbation method (GPM) in the linear muffin tin orbital basis. The reference medium for the GPM is chosen as the completely disordered state of the alloy, with its electronic structure described via the coherent potential approximation. The effective pair interactions are used to obtain the ordered superlattice structures and to estimate the order-disorder transition temperatures. The tendency of primary ordering to the B2 structure and secondary ordering to the DO3 structure is examined as a function of Fe concentration. We find that the tendency to B2 (CsCl) ordering decreases in sequence from the paramagnetic to the DLM's and to the ferromagnetic model. The tendency to secondary ordering in the DO3 structure is strongest in the ferromagnetic model and is found to increase with Fe concentration due to enhanced spin polarization. Factors such as lattice relaxation, charge transfer, and alloy volume (per atom) are found to be much more important for secondary than for primary ordering. Although the model provides a way to study the ordering tendency in the alloy based on an ab initio electronic structure calculation, it is deficient in capturing all the intricacies of the interplay between magnetic and chemical structure. Effects of spin fluctuations on the order-disorder transition are also neglected.
引用
收藏
页码:8184 / 8193
页数:10
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