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Studies on Electronic Structure of p Electron Systems and Nanostructure Materials Based on First-Prinsiples Methods for Strongly Correlated Electrons

基于强关联电子第一性原理方法的p电子体系和纳米结构材料的电子结构研究

基本信息

批准号：
16340100
负责人：
IMADA Masatoshi
金额：
$ 5.63万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2007
项目状态：
已结题

项目摘要

The goal of this project is to develop a hybrid computational method for electronic structure calculations of strongly correlated electron systems by combining the density functional theory and solvers for models of strongly correlated lattice models. By establishing the method, we apply it to p electron systems and nanostructure materials. This hybrid method consists of the following three procedures: (1) Calculate global electronic band structure by the density functional theory using the local density approximation and GW approximation (2) Eliminate and trace out the high-energy scale by downfolding and derive low-energy effective models (3) Solve the low-energy models by reliable low-energy solvers. This scheme has been applied to Sr2VO4. We have revealed that Sr2VO4 is near the metal-insulator phase boundary with antiferromagnetic order and shows complicated spin-orbital orders. Next we have applied to electronic structure calculation of YVO3. It shows the insulating ground state … More with the gap given by 0.9 eV, which is in agreement with the experimental gap, 1.0eV. Based on these successful results, we have applied this scheme to p-electron systems. In p-electron systems, we have employed the plane-wave basis. This has been applied to an organic conductor, BEDT-TTF compound and we have derived the low-energy effective Hamiltonian. We have also examined the efficiency for excitation spectra. The downfolding scheme has been applied to GaAs and LiF and the optical conductivity has been calculated. These results show that excitonic effects are correctly captured by this scheme. In this project, several different types of low-energy solvers have also been developed. In addition to the path integral renormalization group, Gaussian basis Monte Carlo and improved variational Monte Cairo methods have been developed and we have clarified that these method may be used as a highly accurate low-energy solver essentially without the minus sign problem. By these achievements, a new type of electronic structure calculation method based on the three-stage scheme for strongly correlated electron systems including p-electron compounds are now well established. Less

这个项目的目标是通过结合密度泛函理论和强关联晶格模型模型的求解器来发展一种计算强关联电子系统电子结构的混合计算方法。通过建立这种方法，我们将其应用于p电子系统和纳米结构材料。该混合方法包括以下三个步骤：(1)利用局域密度近似和GW近似，用密度泛函理论计算全球电子能带结构；(2)通过向下折叠消除和追踪高能尺度，得到低能有效模型；(3)用可靠的低能求解器求解低能模型。该方案已应用于Sr2VO4。我们发现，Sr2VO4在金属-绝缘体相界附近具有反铁磁有序，并表现出复杂的自旋-轨道有序。接下来，我们将其应用于YVO_3的电子结构计算。它显示了绝缘基态…与0.9 eV给出的间隙更接近，与实验得到的1.0 eV的间隙一致。基于这些成功的结果，我们将该方案应用于p电子系统。在p电子系统中，我们采用了平面波基。将其应用于有机导体BEDT-TTF化合物，得到了低能有效哈密顿量。我们还考察了激发光谱的效率。将下折叠方法应用于GaAs和LiF，计算了它们的光学电导率。这些结果表明，该方案正确地捕获了激子效应。在这个项目中，还开发了几种不同类型的低能量求解器。除了路径积分重整化群外，还发展了高斯基蒙特卡罗方法和改进的变分蒙特卡罗方法，并阐明了这些方法基本上可以作为一种高精度的低能量求解器，而不存在负号问题。通过这些成果，建立了一种基于三阶段方案的新型电子结构计算方法，该方法适用于包括p电子化合物在内的强关联电子系统。较少