单轴应变条件下Fe从α到ε结构相变机制的第一性原理计算  

The mechanism of structure phase transition from α Fe to ε Fe under uniaxial strain: First-principles calculations

作　　者：卢志鹏[1,2,3] 祝文军[1,2] 卢铁城[2] 刘绍军[4] 崔新林[1] 陈向荣[2] 

机构地区：[1]中国工程物理研究院流体物理研究所冲击波物理与爆轰物理国防科技重点实验室,绵阳621900 [2]四川大学物理科学与技术学院,成都610064 [3]中国人民武装警察部队成都指挥学院,成都610213 [4]北京师范大学物理系,北京100875

出　　处：《物理学报》2010年第6期4303-4312,共10页Acta Physica Sinica

基　　金：冲击波物理与爆轰物理国防科技重点实验室基金(批准号:9140C67010106ZS75);中国工程物理研究院科学技术基金重点项目(批准号:2007A01004);国家自然科学基金(批准号:10576004,10776022)资助的课题~~

摘　　要：采用基于密度泛函理论的平面波赝势方法,研究了沿[001]方向单轴应变条件下Fe从体心立方结构(bcc,α相)到六角密排结构(hcp,ε相)相变的临界压力、相变路径、相变势垒以及相变过程中原子磁性的变化.结果发现:单轴应变条件下Fe从α到ε结构的相变路径与以前理论计算模拟给出的静水压力条件下的相变路径明显不同;原子磁矩沿着相变路径突然降低,同时伴随着能量和体积的突然变化,是典型的一阶磁性相转变,表明原子磁性的丧失导致了bcc结构不稳定而向hcp结构转变.对单轴应变下吉布斯自由能的计算表明,相变势垒随着单轴应变的增加(压力的增加)而降低.同时还就单轴应变条件对相变影响的物理机制进行了讨论.We performed first-principles calculations for the pressure-induced martensitic phase transition from the ground state ferromagnetic body-center cubic （bcc） phase to a nonmagnetic hexagonal close-packed （hcp） phase of Fe under uniaxial strain along the [001]direction of bcc phase based on density-functional theory,employing the pseudopotentional and plane-wave method. The calculated results show that the transition path under unixial strain is significantly different from that under hydrostatic pressure. A sudden drop of the magnetic moment is observed at a critical point on the transition path,which results in a discontinuous derivative in the total energy and volume curve. This is a feature of a magnetic first-order phase transition,which indicates that magnetism is the primary stabilizing mechanism of the bcc structure. The enthalpy barrier for bcc-to-hcp transformation decreases as the uniaxial strain （ the pressure） increases. The physical origin of the influence of uniaxial strain on the phase transition is discussed.

关 键 词：相变 单轴应变 第一性原理 铁 

分 类 号：O481[理学—固体物理]