第一性原理计算:MgCNi_3镁位空穴(Na)掺杂的声子谱研究  

IFIRST-PRINCIPLES CALCULATIONS:INVESTIGATION OF PHONON SPECTRUM IN Na-DOPED MgCNi_3

作　　者：舒华兵[1] 王玮[1] 刘楣[1] 

机构地区：[1]东南大学物理系,南京210096

出　　处：《低温物理学报》2009年第2期113-118,共6页Low Temperature Physical Letters

基　　金：高等学校博士学科点专向科研基金(批准号:20060286044)资助的课题~~

摘　　要：应用全势线性响应线性糕模轨道(FP-LR-LMTO)方法对MgCNi3镁位进行钠掺杂的虚原子近似,计算晶格振动的动力学矩阵,得到Mg1-xNaxCNi3(x=0,0.06)的声子谱.计算结果表明MgCNi3声子谱中最低声学支沿Г-M方向有接近一半距离的不稳定声子模存在,不稳定声子模都包括在原胞内x-y平面上两个相邻Ni原子沿着与C-Ni键垂直的方向上,向着镍八面体间隙区的垂直运动x为0.06的掺杂,使得布里渊区沿三个主要高对称性方向(Г-x、Г-M、Г-R)虚频范围扩大,容易使MgCNi3结构不稳定而产生结构相变.Using the full-potential linear-muffin-tin-orbital programs and the linear-response linear-muffin-tin- orbital programs, we calculate the dynamics matrix of vibrations in crystal lattices, and study the phonon spectrum in Na-doped Mg1-xNa,CNi3（x=0,0.06）. It is found that there is unstable phonon mode near half distance along direetion in the lowest acoustics braneh of the phonon spectrum of MgCNi3. Nearly un- stable phonon modes exist when each of the two Ni atoms on the x-y plane movies toward oetahedral inter- stitial sites along vertical direction with C-Ni bond. Study of phonon vibration in Na-doped Mg1-x NaxCNi3（x= 0.06） suggests that the loosened crystal lattices bring more virtual frequency along the three major high symmetry lines（Г-x,Г-M,Г-R ） of the eubie Brillouin zone. The loosened crystal lattices easily make MgCNi3 give birth to unstable structure, and can bring structural phase ehange.

关 键 词：MGCNI3 晶格振动 声子谱 掺杂 

分 类 号：O483[理学—固体物理]