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Theoretical Study on Electronic Band Structureand Physical Properties if Ternary Compounds

三元化合物电子能带结构及物理性质的理论研究

基本信息

批准号：
04640339
负责人：
SUZUKI Naoshi
金额：
$ 1.34万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

项目摘要

Electronic vand strucurures and total energies are calculated for intercalated compounds A_xTiS_2 (A = transition-metals, silver, and alkaline metals) and trnary intermetallic compounds Mn_2Sb, Mn_3GaC, and Fe_7Se_8 by using the LAPW method.1. A_xTiS_2 (A = transition-metals, silver, and alkaline metals) For the silver-intercalated compound Ag_x TiS_2 the selectronic states of silver atoms hybridize strongly with those of the host material, but a cohesive energy gain due to the hybrideization is rather small. On the other hand, the alkaline metal atoms only donate electrons to the host material. The chemical bonds between guest atoms and the host material are relatively weak for Ag_xTiS_2 and the alkline-metal-intercalated compounds compared with the transition-metal-intercalated compounds. From the total energy calculation it is confirmed that the ABC-stacking structure is more stable than the AB-stacking is favorable for Ag_xTiS_2.2. Ternary intermetallic compounds Mn_2Sb, Mn_3GaC, and Fe_7Se_8 (1) Mn_2Sb : From the total energies calculated as a function of the lattice constants, a and c, it is found that the ferrimagnetic state is more stable than the antiferromagnetic state. The evaluated value of the linear compressibility along the a-axis is larger than that along the c-axis. (2) Mn_3GaC : It is found that both the magnitude of the magnetic moment at each maganese site and its volume dependence are larger for the antiferromagnetic state than those for the ferromagnetic state. Further, the antiferromagnetic phase becomes more stable than the ferromagneric state in larger volume side. (39 Fe_7Se_8 : In the ferrimagnetic state, the magnetic moments at crystallographically inequivalent iron sites have almost the same values with each other. The photoemission and the optical conductivity spectra clculated from the electronic density of states are in good correspondence with the observations.

用LAPW方法计算了插层化合物A_xTiS_2（A =过渡金属、银和碱金属）和三元金属间化合物Mn_2Sb、Mn_3GaC和Fe_7Se_8的电子结构和总能量. A_xTiS_2（A =过渡金属、银和碱金属）对于银插层化合物Ag_xTiS_2，银原子的选择电子态与主体材料的选择电子态强烈杂化，但由于杂化而产生的内聚能增益相当小。另一方面，碱金属原子仅向主体材料提供电子。与过渡金属插层化合物相比，Ag_xTiS_2和碱金属插层化合物的客体原子与主体材料之间的化学键相对较弱。从总能量计算中证实了ABC堆积结构比AB堆积结构更稳定，有利于Ag_xTiS_2。三元金属间化合物Mn_2Sb、Mn_3GaC和Fe_7Se_8（1）Mn_2Sb：从计算的总能量作为晶格常数a和c的函数，发现亚铁磁态比反铁磁态更稳定。沿沿着a轴的线性压缩率的评估值大于沿沿着c轴的线性压缩率的评估值。(2)Mn_3GaC：结果表明，反铁磁态的各锰位磁矩的大小及其体积依赖性均大于铁磁态。此外，反铁磁相变得比铁磁态更稳定，在较大的体积侧。(39 Fe_7Se_8：在亚铁磁状态下，晶体学上不等价的铁位置处的磁矩彼此具有几乎相同的值。由电子态密度计算得到的光电导谱和光电导谱与观测结果符合较好。