GMR effect of multilayers of bcc-Fe(M)(M=Co, Ni) alloy and Cu layers has been investigated. The maximum MR ratio is found at 1.1 nm Fe(Co) and 1.3～1.4 nm Cu layer thickness in [Fe(Co)/CuJ, and at 1.6 nm Fe(Ni) and 1....GMR effect of multilayers of bcc-Fe(M)(M=Co, Ni) alloy and Cu layers has been investigated. The maximum MR ratio is found at 1.1 nm Fe(Co) and 1.3～1.4 nm Cu layer thickness in [Fe(Co)/CuJ, and at 1.6 nm Fe(Ni) and 1.4 nm Cu layer thickness in [Fe(Ni)/Cu]. Under the optimum annealing condition, the MR ratio increases up to 50% and 38% for Fe(Co) and Fe(Ni) systems, respectively. The origin of the increase of GMR is discussed, taking the progress of preferred orientation of Fe(Co)[100] or Fe(Ni)[100] by anneahng into account.展开更多
采用基于密度泛函理论(DFT)的第一性原理,研究了Ni对bcc-Fe/ε-Cu界面结合的影响。建立了ε-Cu在bcc-Fe的析出模型,选取界面两侧不同阵点位置,计算Ni在不同位置的偏聚能,分析了Ni在界面区域的占位倾向,在此基础上探究了Ni对bcc-Fe/ε-C...采用基于密度泛函理论(DFT)的第一性原理,研究了Ni对bcc-Fe/ε-Cu界面结合的影响。建立了ε-Cu在bcc-Fe的析出模型,选取界面两侧不同阵点位置,计算Ni在不同位置的偏聚能,分析了Ni在界面区域的占位倾向,在此基础上探究了Ni对bcc-Fe/ε-Cu界面结合的影响。利用Rice-Wang热力学模型的计算表明,当Ni原子处于偏聚能最低的位置时,能够强化界面的结合。而界面分离功计算结果显示,Ni偏聚于bcc-Fe/ε-Cu界面后,界面分离功由279.8 m J·m^(-2)增加到286.7 m J·m^(-2),表明Ni偏聚后会使界面体系更加稳定。Ni偏聚于界面后对界面区域的电子结构也产生一定影响,差分电荷密度显示,与纯bcc-Fe/ε-Cu界面相比,Ni偏聚后会在其周围聚集较多的电子,且Ni与相邻原子之间电子云方向性更为明显;同时,Ni也使近邻Cu和Fe原子的态密度(DOS)向成键态偏移,这使得Ni偏聚加强了bcc-Fe/ε-Cu界面的结合,使界面区更为稳定。展开更多
Oxidation corrosion of steels usually occurs in contact with the oxygen-contained environment, which is accelerated by high oxygen concentration and irradiation. The oxidation mechanism of steels is investigated by th...Oxidation corrosion of steels usually occurs in contact with the oxygen-contained environment, which is accelerated by high oxygen concentration and irradiation. The oxidation mechanism of steels is investigated by the adsorption/solution of oxygen atoms on/under body-centered-cubic(bcc) iron surfaces, and diffusion of oxygen atoms on the surface and in the near-surface region. Energetic results indicate that oxygen atoms prefer to adsorb at hollow and long-bridge positions on the Fe(100) and(110) surfaces, respectively. As the coverage of oxygen atoms increases, oxygen atoms would repel each other and gradually dissolve in the near-surface and bulk region. As vacancies exist, oxygen atoms are attracted by vacancies, especially in the near-surface and bulk region. Dynamic results indicate that the diffusion of O atoms on surfaces is easier than that into near-surface, which is affected by oxygen coverage and vacancies. Moreover, the effects of oxygen concentration and irradiation on oxygen density in the near-surface and bulk region are estimated by the Mc Lean’s model with a simple hypothesis.展开更多
A molecular dynamics model has been developed to investigate the evolution of the internal crack of nano scale during heating or compressive loading in BCC Fe. The initial configuration does not contain any pre-existi...A molecular dynamics model has been developed to investigate the evolution of the internal crack of nano scale during heating or compressive loading in BCC Fe. The initial configuration does not contain any pre-existing dislocations. In the case of heating, temperature shows a significant effect on crack evolution and the critical temperature at which the crack healing becomes possible is 673 K. In the case of compressive loading, the crack can be healed at 40 K at a loading rate 0.025 × 1018 Pa·m1/2/s in 6 × 10-12 s. The diffusion of Fe atoms into the crack area results in the healing process. However, dislocations and voids appear during healing and their positions change continuously.展开更多
基金Ministry of Education, Science, Sports and Culture under Grantin-Aid for Scielltific Research on Priority Areas (A), Japan!(No.
文摘GMR effect of multilayers of bcc-Fe(M)(M=Co, Ni) alloy and Cu layers has been investigated. The maximum MR ratio is found at 1.1 nm Fe(Co) and 1.3～1.4 nm Cu layer thickness in [Fe(Co)/CuJ, and at 1.6 nm Fe(Ni) and 1.4 nm Cu layer thickness in [Fe(Ni)/Cu]. Under the optimum annealing condition, the MR ratio increases up to 50% and 38% for Fe(Co) and Fe(Ni) systems, respectively. The origin of the increase of GMR is discussed, taking the progress of preferred orientation of Fe(Co)[100] or Fe(Ni)[100] by anneahng into account.
文摘采用基于密度泛函理论(DFT)的第一性原理,研究了Ni对bcc-Fe/ε-Cu界面结合的影响。建立了ε-Cu在bcc-Fe的析出模型,选取界面两侧不同阵点位置,计算Ni在不同位置的偏聚能,分析了Ni在界面区域的占位倾向,在此基础上探究了Ni对bcc-Fe/ε-Cu界面结合的影响。利用Rice-Wang热力学模型的计算表明,当Ni原子处于偏聚能最低的位置时,能够强化界面的结合。而界面分离功计算结果显示,Ni偏聚于bcc-Fe/ε-Cu界面后,界面分离功由279.8 m J·m^(-2)增加到286.7 m J·m^(-2),表明Ni偏聚后会使界面体系更加稳定。Ni偏聚于界面后对界面区域的电子结构也产生一定影响,差分电荷密度显示,与纯bcc-Fe/ε-Cu界面相比,Ni偏聚后会在其周围聚集较多的电子,且Ni与相邻原子之间电子云方向性更为明显;同时,Ni也使近邻Cu和Fe原子的态密度(DOS)向成键态偏移,这使得Ni偏聚加强了bcc-Fe/ε-Cu界面的结合,使界面区更为稳定。
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2017YFE0302400 and 2017YFA0402803)the National Nature Science Foundation of China(Grant Nos.11735015,52071314,51871207,U1832206,12075274,U1967211,52171084)Hefei Advanced Computing Center。
文摘Oxidation corrosion of steels usually occurs in contact with the oxygen-contained environment, which is accelerated by high oxygen concentration and irradiation. The oxidation mechanism of steels is investigated by the adsorption/solution of oxygen atoms on/under body-centered-cubic(bcc) iron surfaces, and diffusion of oxygen atoms on the surface and in the near-surface region. Energetic results indicate that oxygen atoms prefer to adsorb at hollow and long-bridge positions on the Fe(100) and(110) surfaces, respectively. As the coverage of oxygen atoms increases, oxygen atoms would repel each other and gradually dissolve in the near-surface and bulk region. As vacancies exist, oxygen atoms are attracted by vacancies, especially in the near-surface and bulk region. Dynamic results indicate that the diffusion of O atoms on surfaces is easier than that into near-surface, which is affected by oxygen coverage and vacancies. Moreover, the effects of oxygen concentration and irradiation on oxygen density in the near-surface and bulk region are estimated by the Mc Lean’s model with a simple hypothesis.
文摘A molecular dynamics model has been developed to investigate the evolution of the internal crack of nano scale during heating or compressive loading in BCC Fe. The initial configuration does not contain any pre-existing dislocations. In the case of heating, temperature shows a significant effect on crack evolution and the critical temperature at which the crack healing becomes possible is 673 K. In the case of compressive loading, the crack can be healed at 40 K at a loading rate 0.025 × 1018 Pa·m1/2/s in 6 × 10-12 s. The diffusion of Fe atoms into the crack area results in the healing process. However, dislocations and voids appear during healing and their positions change continuously.
