多体格林函数理论是研究复杂化学体系电子激发态非常有效的第一性原理方法。介电函数是多体格林函数理论中描述电子相关作用的关键物理量，本项目将发展新的计算方法和程序以提高该物理量的计算效率，从而可以高效地研究复杂化学体系的激发态。此外，我们将进一步改进我们自己发展起来的计算激发态作用力的方法和程序，通过发展计算电子自能算符导数的新方法和程序，在多体格林函数理论框架内更加精确、高效地计算激发态作用力。应用我们所发展的方法和程序，研究半导体光催化剂表面水光解和二氧化碳光还原的激发态动力学过程。通过比较几类典型光催化剂，揭示这两类太阳光能量转换过程中光催化剂各物理参数调控反应路径和产物选择性的机制，重点探索介质及固/液界面在反应中所起的作用，弄清这两类光化学反应中的一些基本科学问题，为研制高效的光催化剂提供理论依据。本课题组从事相关研究多年，有很好的工作基础，通过进一步努力可望取得较大突破。

Many-body Green’s function theory (MBGFT), which includes GW method and Bethe-Salpeter equation, is a state-of-the-art first-principles approach to study electronic excited states in complex chemical systems. Dielectric function is the fundamental physical quantity to describe electronic correlation interactions within MBGFT and is also the most time-consuming part in the calculation. In order to enhance the efficiency of excited-state calculations for complex chemical systems by MBGFT, in this project new computational methods and codes will be developed to accelerate the calculation of dielectric function. We will also improve the theoretical methods and codes for the evaluation of excited-state forces which we have developed within MBGFT; in this respect, new methods and codes will be developed to compute derivatives of the electronic self-energy operator with respect to nuclear positions so as to increase the accuracy of excited-state forces. These new methods and codes will be employed to study the excited-state dynamics in the water photolysis and CO2 photoreduction processes on the surfaces of semiconductor photocatalysts. Through comparing some typical photocatalysts, we will try to uncover the mechanism behind the modulation of reaction path and products selectivity by the physical parameters of photocatalysts in these two solar energy conversion processes. Particular attention will be paid to the role of aqueous environment and solid/liquid interface in the reactions. Through these studies, we hope to understand some basic scientific problems in these two photochemical reactions and to provide some theoretical bases for the development of high-quality photocatalysts for water photolysis and CO2 photoreduction. Our group has undertaken related researches for many years, has good experiences and could achieve big breakthrough through further efforts.