MnPd合金相变,弹性和热力学性质的第一性原理研究  

Ab initio calculation of phase transitions,elastic,and thermodynamic properties of MnPd alloys

作　　者：张炜[1] 陈文周[2] 王俊斐[2] 张小东[2] 姜振益[2] 

机构地区：[1]西安邮电大学理学院,西安710121 [2]西北大学现代物理研究所,西安710069

出　　处：《物理学报》2012年第24期420-425,共6页Acta Physica Sinica

基　　金：国家自然科学基金(批准号:10647008;50971099);高等学校博士学科点专项科研基金(批准号:20096101110017);陕西省自然科学基础研究计划重点项目(批准号:2010JZ002)资助的课题~~

摘　　要：运用基于密度泛函理论第一性原理方法研究了MnPd从立方顺磁到四方反铁磁的相变以及其弹性性质和热力学性质等.结果表明:MnPd合金顺磁立方B2结构在施加了四方应变后,结构不稳定,会发生结构相变形成四方顺磁结构.四方顺磁相弹性稳定,然而在考虑了磁性后,反铁磁四方相比四方顺磁相能量更低,而且弹性和动力学都稳定,说明反铁磁四方相是MnPd的低温结构.从而得出MnPd合金的相变路径为两步:先发生结构相变从顺磁B2立方结构转变为顺磁四方相,再由磁性诱发相变形成反铁磁四方结构.通过准谐近似得到了摩尔比热容,徳拜温度等热力学性质.The phase transitions, elastic and thermodynamic properties of MnPd are investigated using first-principles calculations. The elastic constant calculations indicate that the paramagnetic cubic structure is unstable to external strain and the softening of C1l-C12 triggers the paramagnetic cubic phase transformation. The paramagnetic tetragonal structure is mechanically and dynamically stable. When considering the magnetic property, a antiferromagnetic tetragonal structure is lower in energy than the paramagnetic tetragonal structure. So we can conclude that the structural behaviors of MnPd alloys change from paramagnetic cubic to paramagnetic tetragonal, and then to antiferromagnetic tetragonal structure. Moreover, we employ quasiharmonic approximation to calculate the heat capacity and the Debye temperature.

关 键 词：弹性 热力学性质 密度泛函理论 

分 类 号：O469[理学—凝聚态物理]