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Theoretical Study of Surface Electronic States of Layered Transition-Metal Dichalcogenides and Scanning Tunneling Spectroscopy

层状过渡金属二硫属化物表面电子态理论研究及扫描隧道光谱

基本信息

批准号：
63540250
负责人：
SUZUKI Naoshi
金额：
$ 0.83万
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：
1988
资助国家：
日本
起止时间：
1988 至 1989
项目状态：
已结题

项目摘要

As a first step toward obtaining surface electronic states or electronic states of a slab of layered transition-metal dichalcogenides TX_2 (T:transition-metal atoms, X:chalcogen atoms), we have calculated the bulk electronic band structures of TX_2 itself and its transition-metal intercalation compounds.We first calculated the bulk electronic band structures of 1T-TiS_2, 1T-TiSe_2, 2H-TaS_2 and 2H-NbS_2 on the basis of the APW method with use of the muffin-tin (MT) approximation. As the result it has been clarified that corrections to the MT approximation are very important for these materials because of their strong anisotropic nature. It has been also clarified that in order to make correction to the MT approximation we have to use linearized methods of the band calculation such as the LAPW method because of a problem of computing time, in particular when calculating the electronic band structures of systems containing many atoms in the unit cell.Next, by using the LAPW method we calculated the electronic band structures of transition-metal intercalation compounds of 2H-TaS_2, Mn_<1/4>TaS_2, which has 26 atoms in the unit cell. The band structures obtained for the non-magnetic states have clearly shown that the localized moment model for the Mn 3d electrons and the rigid band model for intercalation effects are not valid. Further the magnitude of the magnetic moment per Mn atom evaluated from the band calculation for the ferromagnetic states is in good agreement with the observation. Thus it has been clarified that the magnetic properties of Mn_<1/4>TaS_2 can be understood from the view point of itinerant Mn 3d electrons.We are now developing LAPW computer programs for making corrections to the MT approximation and for calculating electronic structures of a slab of TX_2.

作为获得层状过渡金属二硫族化物TX_2（T：过渡金属原子，X：硫族原子）的表面电子态或电子态的第一步，我们计算了TX_2本身及其过渡金属插层化合物的体电子能带结构。我们首先计算了1T-TiS_2、1T-TiSe_2的体电子能带结构， 2H-TaS_2 和 2H-NbS_2 基于 APW 方法并使用松饼罐 (MT) 近似。结果表明，由于这些材料具有很强的各向异性，因此对 MT 近似的修正非常重要。还明确了，为了对 MT 近似进行修正，由于计算时间的问题，我们必须使用线性化的能带计算方法，例如 LAPW 方法，特别是在计算晶胞中包含许多原子的系统的电子能带结构时。接下来，通过使用 LAPW 方法，我们计算了 2H-TaS_2 过渡金属插层化合物的电子能带结构， Mn_1/4TaS_2，晶胞中有26个原子。非磁态获得的能带结构清楚地表明，Mn 3d 电子的局域矩模型和插层效应的刚性能带模型是无效的。此外，从铁磁态能带计算中评估的每个 Mn 原子磁矩的大小与观察结果非常一致。由此表明，Mn_<1/4>TaS_2的磁性可以从流动的Mn 3d电子的角度来理解。我们现在正在开发LAPW计算机程序，用于修正MT近似并计算TX_2板的电子结构。