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arXiv 1407.5013cond-mat.mtrl-sci
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Be-Fe-Al金属间化合物的晶体结构、热力学、磁学和无序性质

Crystal structure, thermodynamics, magnetics and disorder properties of Be-Fe-Al intermetallics

Patrick A. Burr, Simon C. Middleburgh, Robin W. Grimes

摘要:

采用密度泛函理论结合声子态密度计算方法研究了Be合金的弹性和磁性、结晶稳定性、偏离化学计量比以及有序/无序相变等温度效应。发现了Be-Fe二元ε相的一种新的结构和组成。在不存在Al时,FeBe_5在~ 1250 K以上形成平衡相,而ε相仅在~ 1650 K以下稳定,FeBe_2在熔点以下的所有温度都稳定。发现少量Al的加入使FeBe_5稳定于FeBe_2和ε,而在高Al含量下,预计会形成AlFeBe_4。偏离化学计量组成也被认为是重要的FeBe_5和ε的情况下。AlFeBe_4(在所有温度下都表现出完全的Al-Fe无序)和FeBe_5(在~ 950 K时表现出有序-无序转变)的无序结构与有序结构的倾向也很重要。

英文摘要:

The elastic and magnetic properties, thermodynamical stability, deviation from stoichiometry and order/disorder transformations of phases that are relevant to Be alloys were investigated using density functional theory simulations coupled with phonon density of states calculations to capture temperature effects. A novel structure and composition were identified for the Be-Fe binary ε phase. In absence of Al, FeBe_5 is predicted to form at equilibrium above ~ 1250 K, while the ε phase is stable only below ~ 1650 K, and FeBe_2 is stable at all temperatures below melting. Small additions of Al are found to stabilise FeBe_5 over FeBe_2 and ε, while at high Al content, AlFeBe_4 is predicted to form. Deviations from stoichiometric compositions are also considered and found to be important in the case of FeBe_5 and ε. The propensity for disordered vs ordered structures is also important for AlFeBe_4 (which exhibits complete Al-Fe disordered at all temperatures) and FeBe_5 (which exhibits an order-disorder transition at ~ 950 K).

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