Mechanical stability of Ni and Ir under hydrostatic and uniaxial loading
Mechanical stability of Ni and Ir under hydrostatic and uniaxial loading
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DOI：
10.1088/0965-0393/23/5/055010
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发表时间：
2015-05
影响因子：
1.8
通讯作者：
P. Řehák;M. Černý;M. Šob
中科院分区：
文献类型：
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作者：
P. Řehák;M. Černý;M. Šob
两个面心立方晶体，镍和铱，受到模拟各向同性和单轴拉伸沿着100纳米？>方向它们的结构稳定性进行了评估，通过分析声子谱，从第一原理计算的不同值的应变。还进行了弹性稳定条件的相关分析。预测的弹性不稳定性对应于那些与软声子消失波矢。虽然大多数以前的研究预测，在晶体中的第一不稳定性对应于宏观（弹性）的不稳定性，我们发现软声子的有限波矢在较低的应变（和应力）在两个考虑的负载在晶体中的Ir。预测的不稳定性证实了我们的微观变形模型。
Two fcc crystals, Ni and Ir, are subjected to simulated isotropic and uniaxial tension along the 〈100〉?> direction. Their structural stability is assessed by analyzing phonon spectra that are calculated from first principles for different values of strain. A relevant analysis of elastic stability conditions is also performed. Predicted elastic instabilities correspond well to those associated with soft phonons with vanishing wavevectors. Although most of previous studies predicted that first instabilities in crystals correspond to macroscopic (elastic) instabilities, we found soft phonons of finite wavevectors at lower strains (and stresses) during both considered loadings in the crystal of Ir. Predicted instabilities were confirmed by our models of microscopic deformation.