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首页> 外文学位 >Metal-insulator transition in vanadium dioxide and titanium oxide using the three-dimensional periodic shell model and DV-X(alpha) cluster method (Japanese text).
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Metal-insulator transition in vanadium dioxide and titanium oxide using the three-dimensional periodic shell model and DV-X(alpha) cluster method (Japanese text).

机译：使用三维周期性壳模型和DV-X（α）簇方法在二氧化钒和二氧化钛中进行金属-绝缘体转变（日语，日语）。

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摘要

The purpose of this study is to calculate electronic structures of the metallic and insulating phases of vanadium dioxide and titanium sesquioxide by using a combination of the three-dimensional periodic shell model and the discrete-variational (DV)-X alpha cluster method. When temperature decreases, vanadium dioxide undergoes a crystallographic phase transition and a metal-insulator (MI) transition at 340K. Unlike the clear cut MI transition in vanadium dioxide, titanium sesquioxide exhibits a broad crossover between a metallic and an insulating state around 450K, which is also an MI transition. Since the DV-X alpha cluster method can calculate the energies of electron states, the combination of the periodic shell model and the cluster method must contain the possibility to clarify the origin of the MI transition in vanadium dioxide and titanium sesquioxide from the energetic point of view. Therefore, the calculation using this combination is of great significance in order to understand the very important phenomena of vanadium dioxide and titanium sesquioxide, particularly the MI transition.; Besides the effects of intersite repulsive nearest neighbor electron-electron (d-d) Coulombic interaction and the spin-spin interaction by means of a generalized Hubbard Hamiltonian, the Hamiltonian in the insulating phase includes Anderson's attractive potential due to the electron-phonon interaction which stabilize the three-dimensional periodic distribution of cation pairs. The shell model estimates the electron-phonon coupling constants and provides direct theoretical evidence that the three-dimensional periodic distribution of cation pairs are stabilized in the insulating phase. In addition, the DV-X alpha cluster method calculates the electron energy in clusters, the values for the intersite repulsive nearest-neighbor d-d interaction, and the spin-spin interaction.; In vanadium dioxide, the electron-phonon interaction effect and the correlation effect for 3d electrons are found to split d band into the empty upper and the occupied lower Hubbard bands and also to result in an obvious energy gap between these bands in the insulating phase. By contrast, the electron correlation effect and the spin correlation effect are found to be mainly responsible for the broad crossover between a metallic and an insulating state in titanium sesquioxide, although there is some contribution from the electron-phonon interaction. The present calculations describe the characteristic phenomenon in these materials.
机译：这项研究的目的是通过使用三维周期壳模型和离散变量（DV）-X alpha聚类方法的组合来计算二氧化钒和倍半氧化钛的金属相和绝缘相的电子结构。当温度降低时，二氧化钒在340K处经历结晶相变和金属-绝缘体（MI）转变。与二氧化钒中的明晰MI过渡不同，倍半氧化钛在450K左右的金属状态和绝缘状态之间表现出较大的交叉，这也是MI过渡。由于DV-Xα团簇方法可以计算电子态的能量，因此，周期壳模型和团簇方法的组合必须包含从能量点阐明二氧化钒和三氧化二钛中MI转变的起源的可能性。视图。因此，使用这种组合进行计算对于理解二氧化钒和倍半氧化钛的非常重要的现象，特别是MI转变具有重要意义。除了通过广义哈伯德·哈密顿量（Hubbard Hamilton）产生的场间排斥最近邻电子-电子（ dd ）库仑相互作用和自旋-自旋相互作用外，处于绝缘相的哈密顿量还包括安德森的吸引电势。电子-声子相互作用可稳定阳离子对的三维周期性分布。壳模型估计了电子-声子耦合常数，并提供了直接的理论依据，证明阳离子对的三维周期性分布在绝缘相中稳定。另外，DV-X alpha簇方法计算簇中的电子能量，站点间排斥最近邻d 相互作用的值以及自旋-自旋相互作用。在二氧化钒中，发现电子-声子相互作用效应和3 d 电子的相关效应将 d 谱带划分为空的上部和占据的Hubbard下部谱带，以及在绝缘阶段在这些频带之间产生明显的能隙。相比之下，尽管电子-声子相互作用有一些贡献，但发现电子相关效应和自旋相关效应是造成三氧化二钛中金属态与绝缘态之间广泛交叉的主要原因。本计算描述了这些材料中的特征现象。

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  • 作者

    Nakatsugawa, Hiroshi.;

  • 作者单位

    Yokohama National University (Japan).;

  • 授予单位 Yokohama National University (Japan).;
  • 学科 Physics Condensed Matter.; Physics Electricity and Magnetism.; Energy.
  • 学位 Ph.D.
  • 年度 1998
  • 页码 135 p.
  • 总页数 135
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 电磁学、电动力学;能源与动力工程;
  • 关键词

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