Spectroscopic Signatures of Molecular Clusters and Molecular Cluster Aggregates Calculated from First Principles

根据第一原理计算的分子簇和分子簇聚集体的光谱特征

• 批准号: 418808568
• 负责人: Professor Dr. Simone Sanna
• 金额: --
• 依托单位: Institut für Theoretische Physik
• 依托单位国家: 德国
• 项目类别: Research Units
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/418808568?language=en
• 关键词: Spectroscopic; Signatures; Molecular; Clusters; Cluster

In the present project, we aim at gaining a thorough understanding of the interplay between atomic structure, electronic configuration and chemical variations of molecular clusters/cluster aggregates and their optical response. The focus is set on the parameter-free determination of the spectroscopic properties of the investigated molecular compounds. Linear and nonlinear optical spectra, IR and Raman spectra and EELS signatures shall be modeled for isolated molecules and periodic molecular crystals. The effect of structural disorder on the optical properties will be modeled with the help of the ground state geometries calculated from first principles within the project C1. We perform calculations at different levels of accuracy, ranging from the independent particle approximation to more refined calculation schemes including quasiparticle effects and the electron-hole interaction. In the first project phase, we have extended our calculation schemes in order to calculate the nonlinear optical susceptibilities within the time-domain, which allow for an efficient calculation of the optical response with adequate accuracy even for extended systems, including molecular crystals. On the one hand, we deal with well-known model systems such as the prototypical adamantane shaped compounds [(RT)4R6] (with R = organic group; T = C, Si, Ge, Sn; E = O, S, Se, Te, NH, CH2, ON•). On the other hand, we address cubane shaped compounds of general formula [(RT)4MxEz], with M = transition metal, and their chemical variations as realized in project area A. Fundamental questions regarding the prerequisites for the optical nonlinearities such as order/disorder, symmetry and chemical composition are explored. Starting with structural data determined in project C1, our project provides the optical response of the investigated systems, thus helping the interpretation of the measurements in areas A and B and inspiring the synthetization of new compounds with tailored optical properties. Thereby our atomistic models offer two crucial advantages. The first advantage is that the optical response is calculated as a function of the incident wavelength. The knowledge of the full optical spectrum will help to establish the correlation between excitation wavelength and optical nonlinearities, and ascertain whether other light sources than IR radiation can be employed to drive the material. A second great advantage of our models is the possibility to calculate the optical response of metastable structures that are not experimentally accessible, such as metastable clusters or ordered structures of amorphous compounds. This allows to disentangle the different effects that simultaneously act to determine the optical response, and address the physical questions concerning the single aspects.

在本项目中，我们的目标是获得一个透彻的理解之间的相互作用的原子结构，电子构型和化学变化的分子团簇/团簇聚集体和它们的光学响应。重点是设置在无参数确定的光谱特性的研究分子化合物。线性和非线性光学光谱、IR和拉曼光谱以及EELS特征应针对孤立分子和周期性分子晶体进行建模。结构无序对光学性质的影响将在项目C1中根据第一性原理计算的基态几何形状的帮助下进行建模。我们在不同的精度水平进行计算，从独立粒子近似到更精细的计算方案，包括准粒子效应和电子-空穴相互作用。在第一个项目阶段，我们已经扩展了我们的计算方案，以计算在时域内的非线性光学折射率，这使得即使对于扩展的系统，包括分子晶体，也可以有效地计算具有足够精度的光学响应。一方面，我们研究了典型的金刚烷型化合物[（RT）4 R6]（R =有机基团; T = C，Si，Ge，Sn; E = O，S，Se，Te，NH，CH_2，ON·）。另一方面，我们讨论了通式[（RT）4 MxEz]的立方烷形化合物，其中M =过渡金属，以及在项目领域A中实现的它们的化学变化。基本问题的先决条件，如有序/无序，对称性和化学成分的光学非线性进行了探讨。从项目C1中确定的结构数据开始，我们的项目提供了所研究系统的光学响应，从而有助于解释区域A和B中的测量结果，并激发合成具有定制光学特性的新化合物。因此，我们的原子模型提供了两个至关重要的优势。第一个优点是光学响应是作为入射波长的函数计算的。全光谱的知识将有助于建立激发波长和光学非线性之间的相关性，并确定是否可以采用IR辐射以外的其他光源来驱动材料。我们的模型的第二个巨大的优势是计算亚稳态结构的光学响应的可能性，这些亚稳态结构在实验上是不可接近的，例如亚稳态簇或非晶化合物的有序结构。这允许解开同时起作用以确定光学响应的不同效应，并解决关于单个方面的物理问题。