磁致伸缩Fe-Ga合金作为一种新的智能材料在传感器和驱动器等方面有广泛的潜在应用。目前，理解这种合金在高Ga成份下各向异性弹性响应和进一步建立其磁致伸缩性能的变化机制是推动Fe-Ga二元合金走向应用的一个挑战性的问题。基于密度泛函理论和大尺度第一原理分子动力学，我们采用非线性和非均匀退火过程模拟研究了高Ga成份下的微观原子结构对Fe-Ga合金弹性各向异性力学性能的影响。研究表明D0₃型结构的形成对四方剪切模量的软化有重要的影响，而对菱方剪切模量的影响可以忽略。铁与最近邻Ga原子的悬键导致杨氏模量的减少以及沿[110]的负泊松比。[110]方向相比[100] 方向有所提高的杨氏模量归结于沿[110]和[100]方向纯铁层和Fe-Ga混合层不同的安排。在高Ga成份区Fe-Ga合金的延展性增加，对磁致伸缩的提高有促进作用。我们还进一步研究了Fe-Ga合金在x～0.19时四方磁致伸缩的突然下降的原因，在原子尺度范围内建立其微观的变化机制，解释了该领域里长期存在的一个疑问。与此同时，我们在基于硬能带模型的理论上，提出了如何优化磁致伸缩Fe-Ga合金的性能，这为促进其工业应用提供了理论指导。论文发表在Acta Mater 61 (2013) 2919和Scientific Report 3 (2013) 3521。

(a) Calculated E_MCA with εz=±1% for Fe_79.7Ga_20.3 (black dash line) and Fe_79.9Ga_18.7Cu_1.6 (red solid line) versus the number of valence electrons in the unit cell. The two vertical lines show positions of their actual N_e, black for Fe_79.7Ga_20.3 and red for Fe_79.9Ga_18.7Cu_1.6. (b) Strain dependent EMCA of Fe_79.7Ga_20.3 (black open triangle) and Fe_79.9Ga_18.7Cu_1.6 (red open circle); the inset shows the atomic configuration of Fe_79.9Ga_18.7Cu_1.6, where golden, green and blue balls represent Fe, Ga and Cu atoms, respectively. (c) Charge difference between Fe_79.9Ga_18.7Cu_1.6 and Fe_79.7Ga_20.3, in a range of ±0.008 eV/?³. (d) Partial density of states of Fe₂, Fe₁,Ga, Fe₁,Cu and Cu atoms in Fe_79.9Ga_18.7Cu_1.6, the purple arrow highlights the nonbonding states of Fe_1,Ga and Fe_1,Cu atoms.

Calculated (red filled circles) x-dependent of 3/2<λ001>, along with the experimental data measured for the quenched samples at room temperature (dark cyan open circle).6 The golden filled circle at x=20.3 represents result for a metastable structure of Fe79.7Ga18.7Cu1.6. The inset shows the strain-dependent total energy and magnetocrystalline anisotropy energy for one configuration of Fe81.25Ga18.75. (b) Calculated x-dependent <c'> (red filled circles) and <b₁> (blue filled circles), along with experimental data of c'(red open circles and triangles) and b₁ (blue open circles).The golden filled circle represents the calculated b1 of a metastable structure of Fe_7.97Ga_18.7Cu_1.6. (c) Calculated x-dependent number of electronic states at the Fermi level in the minority spin channel, N(E_F,↓). The inset shows the projected density of states (PDOS) of Fe₁, Fe₂ atoms in Fe_81.25Ga_18.75, along with the shaded region for the PDOS of the bcc bulk Fe. (d) Number of D0₃ (black open circles) and B₂ (×30, purple filled circles) pairs. The insets show Fe (golden balls) and Ga (green balls) atoms in the D0₃ and B2 structures.