冲击压缩下金属钯的结构相变  

Phase transitions of palladium under dynamic shock compression

作　　者：刘泽涛 陈博 令伟栋 包南云 康冬冬[1] 戴佳钰[1] Liu Ze-Tao;Chen Bo;Ling Wei-Dong;Bao Nan-Yun;Kang Dong-Dong;Dai Jia-Yu(Department of Physics,National University of Defense Technology,Changsha 410073,China)

机构地区：[1]国防科技大学物理系,长沙410073

出　　处：《物理学报》2022年第3期266-274,共9页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:11774429,12104507);NSAF联合基金(批准号:U1830206);国家重点研发计划(批准号:2017YFA0403200);中国博士后科学基金(批准号:2019M664024)资助的课题.

摘　　要：钯作为典型高压标定材料,研究其在极端条件下的结构变化以及热力学性质具有广泛需求并充满了挑战,特别是冲击加载下钯的固-固相变过程研究仍然匮乏.本文基于嵌入原子势,使用经典分子动力学方法从原子角度揭示了冲击载荷加载下钯的结构相变路径,在0-375 GPa的压力区间观察到一系列复杂的结构转变特征,从初始的面心立方(FCC)结构,至带密排六方(HCP)结构的层错体心立方(BCC)结构,直至完全熔化.在沿<100>晶向冲击下,在70.0 GPa发现了FCC-BCC相变过程,远低于之前研究中静高压的结果.此外,还发现了冲击方向依赖的相变点,在沿着<110>及<111>晶向冲击时FCC-BCC相变压力分别增加至135.8和165.4 GPa,同时相比完美晶体,引入缺陷会使FCC-BCC相变压强值有20-30 GPa的增幅,并通过势能分布的分析予以验证.本文发现冲击加载下钯的FCC-BCC相变压力大大降低的特殊现象,为钯在高压实验等极端条件下的应用提供了新的理论认识.For palladium(Pd) as a typical high-pressure standard material,studying its structural changes and thermodynamic properties under extreme conditions is widely demanded and challenging.Particularly,the solid-solid phase transition process of Pd under shock loading is understood still scarcely.In this paper,using the classical molecular dynamics simulations with embedded atom method(EAM) based on the interatomic potential,we investigate the phase transition of single crystal Pd from atomic scale under shock loading.A series of structural features is observed in a pressure range of 0-375 GPa,revealing that the structure feature transforms from the initial face-centered cubic(FCC) structure to the stacking faults body-centered cubic(BCC) structure with hexagonal close-packed(HCP) structure,and finally complete melting.Under shock loading of <100> oriented bulk Pd,we find the transformation to BCC structure can take place almost at 70.0 GPa,which is much lower than the previous static calculation result.In addition,we find that the phase transition depends on the direction initially impacting crystal.Under impacting along the(110) direction and the <111> direction,the FCC-BCC phase transition pressures increase to 135.8 GPa and 165.4 GPa,respectively.Also,the introduction of defects will increase the phase transition pressure of FCC-BCC by 20-30 GPa in comparison with perfect crystals,which is verified by the distribution of the potential energy.An interesting phenomenon that FCC-BCC transition pressure of Pd decreases under shock loading is found in this work,which provides a new theoretical insight into the application of high pressure experiments in the future.

关 键 词：钯 冲击压缩 分子动力学模拟 结构相变 

分 类 号：TG146.36[一般工业技术—材料科学与工程]