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

本项目的目标是通过结合密度泛函理论和强关联晶格模型的求解器，开发一种用于强关联电子系统的电子结构计算的混合计算方法。通过建立该方法，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）利用密度泛函理论，在局域密度近似和GW近似下计算整体电子能带结构（2）通过下折消除和追踪高能尺度，得到低能有效模型（3）利用可靠的低能求解器求解低能模型。该方案已被应用到Sr 2 VO 4。我们发现Sr_2VO_4在金属-绝缘体相界附近具有反铁磁有序，并显示出复杂的自旋轨道有序。接下来我们应用于YVO 3的电子结构计算。它显示了绝缘基态 关于我们 给出的差距为0.9 eV，这与实验间隙1.0 eV一致。基于这些成功的结果，我们已经将该方案应用到p电子系统。在p电子系统中，我们采用了平面波基。这已应用于有机导体BEDT-TTF化合物，并且我们推导出了低能有效汉密尔顿。我们还研究了激发光谱的效率。下折方案已被应用到GaAs和LiF和光学电导率已被计算。这些结果表明，激子效应是正确的捕获该计划。在这个项目中，还开发了几种不同类型的低能耗求解器。除了路径积分重整化群，高斯基Monte Carlo和改进的变分Monte Cairo方法已经开发出来，我们已经澄清，这些方法可以用作一个高精度的低能量求解器基本上没有负号的问题。通过这些研究成果，建立了一种新的基于三阶段方案的强关联电子体系（包括p电子化合物）的电子结构计算方法。少

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