Structure, energetics, and mechanical stability of Fe-Cu bcc alloys from first-principles calculations
Structure, energetics, and mechanical stability of Fe-Cu bcc alloys from first-principles calculations
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DOI：
10.1103/physrevb.72.144109
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发表时间：
2005-10-01
影响因子：
3.7
通讯作者：
Asta, M
中科院分区：
文献类型：
--
作者：
Liu, JZ;van de Walle, A;Asta, M
基于团簇展开框架，通过从头算研究了体心立方结构的Fe₁₋ₓCuₓ固溶体的原子体积、磁矩、混合能以及弹性性质。对于无序固溶体中与浓度相关的弹性模量的计算，我们引入了一种团簇展开技术的推广形式，该形式旨在处理高对称相中的张量性质。计算得到的混合能、原子体积和磁矩与通过非平衡加工技术制备的亚稳态合金的现有测量结果吻合良好。此外，还计算了无序体心立方相的体模量以及剪切模量C₋₄₄和C₋′随铜浓度的变化。虽然体模量和C₋₄₄在所有浓度下均为正值，但预测C₋′仅在铜浓度小于50原子%时为正，否则为负。因此，我们的结果表明体心立方结构的铜在较宽的成分范围内都存在力学不稳定性。结合观察到的体心立方结构的Fe - Cu合金的亚稳态以及α - Fe基体中纳米级体心立方析出物的强化机制，对本研究结果的意义进行了讨论。
Atomic volumes, magnetic moments, mixing energies, and the elastic properties of bcc Fe1-xCux solid solutions are studied by ab initio calculations based on the cluster expansion framework. For the calculation of concentration-dependent elastic moduli in disordered solid solutions, we introduce a generalization of the cluster expansion technique that is designed to handle tensorial quantities in high-symmetry phases. Calculated mixing energies, atomic volumes, and magnetic moments are found to be in good agreement with available measurements for metastable alloys prepared through nonequilibrium processing techniques. Additionally, the predicted variations of the bulk modulus and shear moduli C-44 and C-' with respect to copper concentration are calculated for the disordered bcc phase. While the bulk modulus and C-44 are positive for all concentrations, C-' is predicted to be positive only for Cu concentration less than 50 atomic %, and negative otherwise. Our results thus indicate that the mechanical instability of bcc Cu persists over a wide range of compositions. The implications of the present results are discussed in relation to the observed metastability of bcc Fe-Cu alloys, and the strengthening mechanism of nanoscale bcc precipitates in an alpha-Fe matrix.