Excitons with time-dependent density-functional theory

该奖项支持理论和计算研究和教育，以开发计算和可视化无机和有机材料光学特性的新方法。一种精确且计算效率高的方法来模拟这些材料的光学特性，将为理解和设计新型太阳能电池和光电子器件提供重要的帮助。这个项目的科学部分将追求两个目标。第一个目标将是开发出能够准确预测大块绝缘体、半导体和新型有机材料对光的吸收的方法。第二个目标是开发一种计算工具，可以可视化复杂有机分子吸收光后带电粒子的动力学。该奖项的教育部分包括对理论和计算凝聚态物质研究的本科生和研究生的培训和指导，本科凝聚态物理和材料科学的课程发展，以及通过参与研究、教学和学习网络整合中心，为科学、技术、工程和数学学科的未来教师做准备。该奖项支持理论和计算研究和教育，以开发基于时间依赖的密度泛函理论的方法，用于计算和可视化无机和有机材料的激子特性。时变密度泛函理论为从第一性原理计算复杂系统的光学性质提供了有效的计算方法。然而，扩展系统提出了许多挑战，特别是局部和梯度校正的交换相关泛函不能描述激子效应。激子需要具有长空间范围的交换相关泛函，到目前为止，这些泛函中只有少数可用于固体。主要的研究目标将是开发和测试在绝缘体和半导体中捕获激子结合的新功能。将追求两个相互关联的研究目标。第一个目标是使用线性响应时变密度泛函理论计算体半导体和绝缘体中的单重态和三重态激子结合能。各种交换相关功能将被实现和测试；研究了基态带结构的影响；非绝热泛函会被开发出来。计算将进行各种无机和有机块状晶体材料和低维系统。第二个研究目标是研究有机分子中的实时激子动力学。将开发一种新的计算工具来可视化激子动力学，即与时间相关的粒子-空穴图，并与现有的计算机代码接口。粒子-空穴图将主要应用于光激发有机给体-受体分子和电荷转移系统的研究。此外，激子的辐射寿命、系统间交叉率和非辐射寿命将被计算。该奖项的教育部分包括对理论和计算凝聚态物质研究的本科生和研究生的培训和指导，本科凝聚态物理和材料科学的课程发展，以及通过参与研究、教学和学习网络整合中心，为科学、技术、工程和数学学科的未来教师做准备。

NONTECHNICAL SUMMARYThis award supports theoretical and computational research and education to develop new approaches for computing and visualizing optical properties of inorganic and organic materials. An accurate and computationally efficient approach to simulate the optical properties of these materials will provide important assistance for understanding and designing novel solar cell and optoelectronic devices.The scientific part of this project will pursue two objectives. The first goal will be to develop methodologies that yield accurate predictions related to the absorption of light by bulk insulators, semiconductors and novel organic materials. The second goal will be to develop a computational tool, which will allow a visualization of the charged particle dynamics following light absorption in complex organic molecules.The educational component of this award consists of the training and mentoring of undergraduate and graduate students in theoretical and computational condensed-matter research, the curricular developments in undergraduate condensed-matter physics and materials science, and the preparation of future faculty in the Science, Technology, Engineering, and Mathematics disciplines via engagement in the Center for the Integration of Research, Teaching and Learning network.TECHNICAL SUMMARYThis award supports theoretical and computational research and education to develop time-dependent density-functional theory based approaches for computing and visualizing excitonic properties in inorganic and organic materials. Time-dependent density-functional theory offers computationally efficient approaches for calculating the optical properties of complex systems from first principles. However, extended systems pose many challenges, in particular, local and gradient-corrected exchange-correlation functionals cannot describe excitonic effects. Excitons require exchange-correlation functionals with a long spatial range, and so far only a few of these have been available for solids. The primary research goal will be to develop and test new functionals which capture excitonic binding in insulators and semiconductors.Two interrelated research objectives will be pursued. The first objective is to use linear-response time-dependent density-functional theory to calculate singlet and triplet exciton binding energies in bulk semiconductors and insulators. A variety of exchange-correlation functionals will be implemented and tested; the influence of the ground-state band structure will be studied; and nonadiabatic functionals will be developed. Calculations will be carried out for a variety of inorganic and organic bulk crystalline materials and low-dimensional systems.The second research objective is to investigate real-time exciton dynamics in organic molecules. A new computational tool to visualize exciton dynamics, the time-dependent particle-hole map, will be developed and interfaced with existing computer codes. The particle-hole map will be mainly applied to study photoexcited organic donor-acceptor molecules and charge-transfer systems that are of interest for application in photovoltaics. In addition, exciton radiative lifetimes, intersystem crossing rates, and nonradiative lifetimes will be computed.The educational component of this award consists of the training and mentoring of undergraduate and graduate students in theoretical and computational condensed-matter research, the curricular developments in undergraduate condensed-matter physics and materials science, and the preparation of future faculty in the Science, Technology, Engineering, and Mathematics disciplines via engagement in the Center for the Integration of Research, Teaching and Learning network.