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Theoretical Study on the Electronic States of Layered Fluorinated Carbon Materials

层状氟化碳材料电子态的理论研究

基本信息

批准号：
13640324
负责人：
KUSAKABE Koichi
金额：
$ 2.18万
依托单位：
NIIGATA UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

项目摘要

We theoretically investigated fluorinated graphite and fluorinated boron-nitrides using the first-principles molecular-dynamics method and clarified that the fluorination of layered graphite and related materials can be utilized as 1) a synthesis method of a wide-gap semiconductor whose band gap is controllable by changing composition and 2) a synthesis method of a nanometer-scale magnet. Major results of our project are summarized as follows.1. Fluorinated graphite C_nF is a layered material whose structure is regarded as a stacking of ultra-thin diamond films with fluorinated surfaces. The material has a direct gap when n=l,2,3, while the gap becomes indirect if n exceeds 4. We proposed that the material may be utilized for fabrication of optical devices including semiconductor LASER and determined wavelengths of expected output theoretically. We proposed that the material is synthesized as a natural superlattice and estimated energy levels of electrons and holes in this 2-dimensional electronic system. Stability and characteristics of (BN)_nF are theoretically predicted.2. We proposed a way to obtain magnetic nanographite from nanometer-scale graphite and finite nanotubes. Existence of magnetism in nanographite, which has been expected by several authors, is shown theoretically. Moreover, it is controllable by chemical treatments including hydrogenation, fluorination and oxygen-substitution of zigzag-edged nanographite in nanometer scale. This is a theoretical prediction of synthesis methods of magnetic materials without magnetic elements.3. New developments in the first-principles electronic-structure calculations including correlation effects were achieved. We proposed an extension of the Kohn-Sham equation. Acceleration of the trans-correlated method is realized.

我们利用第一性原理分子动力学方法对氟化石墨和氟化硼氮化物进行了理论研究，并阐明了层状石墨及相关材料的氟化可以用作1）通过改变组成控制带隙的宽带隙半导体的合成方法和2）纳米级磁体的合成方法。本课题的主要研究成果如下： 1．氟化石墨C_nF是一种层状材料，其结构被视为表面氟化的超薄金刚石膜的堆叠。当n=1、2、3时，该材料具有直接间隙，而当n超过4时，该间隙变为间接间隙。我们提出，该材料可用于制造包括半导体激光器在内的光学器件，并在理论上确定预期输出的波长。我们建议将该材料合成为天然超晶格，并估计该二维电子系统中电子和空穴的能级。对(BN)_nF的稳定性和特性进行了理论预测。 2．我们提出了一种从纳米级石墨和有限纳米管获得磁性纳米石墨的方法。理论上，纳米石墨中存在磁性，这是几位作者所期望的。此外，它可以通过纳米尺度的锯齿形纳米石墨的氢化、氟化和氧取代等化学处理来控制。这是对无磁性元素磁性材料合成方法的理论预测。 3．包括相关效应在内的第一性原理电子结构计算取得了新进展。我们提出了 Kohn-Sham 方程的扩展。实现了互相关方法的加速。