【摘要】 应用全势线性响应线性糕模轨道方法,对MgCNi3镁位进行钠掺杂的虚原子近似,计算Mg1-xNaxCNi3(x=0.0,0.06,0.11,0.115,0.12)的电子态密度和晶格振动(x=0.0,0.06),并讨论磁性和声子谱.计算结果表明,随着掺杂量x的增加,原胞磁矩迅速增加,在x=0.115时,费米能级处总态密度几乎落在范霍夫奇异峰峰顶上且有较大的自旋涨落,预示MgCNi3处在铁磁不稳定的边缘.x=0.12的费米面处总态密度与x=0.115相比有较大的下降,使得超导库珀对配对数减少,会带来超导电性的降低.x为0.06的钠掺杂,使得布里渊区沿三个主要高对称性方向(Γ-X、Γ-M、Γ-R)虚频范围扩大,容易使MgCNi3结构不稳定而产生结构相变。更多还原

【Abstract】 Using the full-potential linear-muffin-tin-orbital programs and the linear-response linear-muffin-tin-orbital programs,we calculate the electronic density of states in Mg1-xNaxCNi3(x=0.0,0.06,0.11,0.115,0.12)and the crystal lattice vibration(x=0.0,0.06),and study their magnetic properties and phonon spectrum.Our results show that the total magnetic moment is enhanced rapidly in the cell with increasing doping.For x=0.115,the total density of states(TDOS)at the Fermi level is nearly located on the top of the van Hovesingularity peak.Besides,the large magnetic fluctuations are found,which indicates that MgCNi3 is near the ferromagnetic phase transition point.For x=0.12,TDOS is lower at the Fermi level than that of x=0.115,making the number of cooper pairs decreased,which may decrease superconductivity.Study of phonon vibration in Na-doped Mg1-xNaxCNi3(x=0.06) suggests that the loosened crystal lattices bring more virtual frequency along three major high symmetry lines(Γ-X 、 Γ-M 、Γ-R)of the cubic Brillouin zone and thus easily bring structural phase change.更多还原