Structural studies of Ni 2+x Mn 1-x Ga by powder x-ray diffraction and total energy calculations
Structural studies of Ni 2+x Mn 1-x Ga by powder x-ray diffraction and total energy calculations
复制标题
DOI：
10.1103/physrevb.75.104107
复制
发表时间：
2007-03
影响因子：
3.7
通讯作者：
S. Banik;R. Ranjan;A. Chakrabarti;S. Bhardwaj;N. Lalla;A. Awasthi;V. Sathe;D. M. Phase;P. Mukhopadhyay;D. Pandey;S. R. Barman
中科院分区：
文献类型：
--
作者：
S. Banik;R. Ranjan;A. Chakrabarti;S. Bhardwaj;N. Lalla;A. Awasthi;V. Sathe;D. M. Phase;P. Mukhopadhyay;D. Pandey;S. R. Barman
用X射线粉末衍射法研究了Ni{sub 2+x}Mn{sub 1-x}Ga的晶体结构与组分（x）的关系。对于Ni{sub 2.24}Mn{sub 0.75}Ga（其中Mn原子的1/4被Ni取代），实验测定的晶格常数与用全势线性缀加平面波方法最小化总能量计算的理论平衡晶格常数符合得很好。当x = 0.15 × 0.35时，在室温下得到一个非调制的四方马氏体相，其晶格常数c随x的增加而线性增加，a随x的增加而线性减小，并遵循Vegard定律。当x=0.2时，退火得到7 M调制的单斜相。马氏体相变滞后的小宽度显示了其热弹性性质，这是形状记忆合金的特征。在室温下观察到0.1{<=}x{<=}0.15的相共存，证实了马氏体相变的一级性质。
The crystal structure of Ni{sub 2+x}Mn{sub 1-x}Ga has been studied as a function of composition (x) by powder x-ray diffraction. For Ni{sub 2.24}Mn{sub 0.75}Ga, where one-fourth of the Mn atoms are replaced by Ni, the experimentally determined lattice constants are in good agreement with theoretical equilibrium lattice constants calculated by minimization of total energy using full potential linearized augmented plane-wave method. For 0.15{<=}x{<=}0.35, a nonmodulated tetragonal martensitic phase is obtained at room temperature, whose lattice constant c increases and a decreases linearly with increasing x following Vegard's law. A 7M modulated monoclinic phase is obtained for x=0.2 due to annealing. The small width of the hysteresis of the martensitic transition shows its thermoelastic nature that is the characteristic of a shape memory alloy. Phase coexistence is observed for 0.1{<=}x{<=}0.15 at room temperature, confirming the first-order nature of the martensitic transition.