Ab-Initio Quantum Simulation of Electoronic Dynamics in Finite Electron System

我们基于时变密度泛函理论（TD-DFT）开发了电子动力学的量子力学和第一性原理模拟。为此，在实时空间和时间上求解了时变的Kohn-Sham方程，这是TD-DFT中的一个基本方程。本课题的研究成果总结如下：1。研究了不同分子和原子团簇的电子激发和光响应。特别是，提出了一种新的非线性光学响应（分子超极化率和双光子吸收）的数值计算方法。本文还提出了一种描述连续态耦合的理论，并将其应用于真空紫外区分子的光吸收。提出了一种求解周期固体介电函数的实时、实空间方法。该方法已应用于简单的金属和绝缘体，并计划扩展到碳纳米管。以苯分子的光吸收光谱为例，考察了TD-DFT在电子-振动耦合中的适用性。描述了离子-原子碰撞中的多重电子转移过程。这有助于我们对电子转移的机理有更深入的了解。开始了强激光场中原子和分子电离机理的研究。建立了液氦原子光谱的理论框架。我们已经在TD-DFT中准备了光响应的FORTRAN代码，并已经分发给那些对使用我们的方法感兴趣的人。

We have developed a quantum mechanical and first principle simulation for electronic dynamics based on the time-dependent density-functional theory ,(TD-DFT). The time-dependent Kohn-Sham equation, which is a basic equation in the TD-DFT, is solved in real-space and -time for this purpose. Results of the present research project are summarized as follows :1. Electronic excitations and optical responses of various moiecuies and atomic clusters are investigated. In particular, a new numerical method for nonlinear optical responses (molecular hyperpolarizabilities and two-photon absorption ) is developed. A theory to describe coupling with continuum states is developed as well, and is applied to optical absorptions of molecules in the vacuum ultraviolet region.2. A real-time and real-space method is developed for the dielectric functions ol periodic solid. The method has been applied to a simple metal and an insulator, and is planned to be extended to carbon nanotubes.3. The applicability of the TD-DFT for electron-vibration coupling is examined taking optical absorption spectrum of benzene molecule as example.3. Multiple electron transfer processes in the ion-atomcollision are described. This helpedus obtaining adeeper understanding on themechanisms of electron transfer.5. Research on ionization mechanism of atoms and molecules in a strong laser field is initiated.6. A theoretical framework for atomic spectra in the liquid helium is developed.7. We have prepared FORTRAN code of optical responses in the TD-DFT, and have been distributing it to those who are interested in using our method.