First principles simulations of electronic spectroscopy for larger molecules

为了详细了解复杂反应中涉及的分子结构，例如在生物学背景下，能够解释各种光谱测量至关重要。对于涉及多个过渡金属原子的系统，可行的光谱学包括共振拉曼、UV-VIS吸收、圆二色性、磁性圆二色性、电子顺磁共振、X射线近边吸收、X射线发射、穆斯堡尔、XPS、NMR和各种时间分辨泵浦-探测技术。光谱的解释是一个复杂的过程，目前通常基于与已知光谱的相似性匹配以及使用简单模型。光谱的解释，也许更重要的是，光谱所暗示的系统的（结构）表征，可以大大有助于可靠的第一原理理论模拟，本建议的主题。在过去，我们已经开发出精确模拟小分子电子光谱的技术。关键成分涉及所谓的振动模型参数提取精确耦合簇型电子结构计算，和量子核运动的多个表面上使用非绝热量子波包动力学的演变。关键的挑战是将我们的方法推广到更大的系统中。我们计划将我们的方法纳入国家的最先进的ORCA电子结构计划，在MPI穆尔海姆的弗兰克尼塞小组开发的鲁尔，并利用本地相关，特别是对自然轨道技术，已被应用于系统大到50-100个原子。此外，ORCA允许我们方便地纳入相对论效应，特别是自旋轨道耦合，这是一个重要的成分，以模拟重要的光谱特性。ORCA将被推广到计算振动模型参数，而非绝热动力学模拟追求采用广泛使用的多组态时间相关哈特里（MCTDH）包，在迈耶集团在海德堡，德国。

To gain a detailed understanding of molecular structures involved in complicated reactions, e.g. in a biological context, it is vital to be able to interpret a variety of spectroscopic measurements. For systems involving multiple transition metal atoms, viable spectroscopies include Resonance Raman, UV-VIS absorption, circular dichroism, magnetic circular dichroism, electron paramagnetic resonance, X-Ray near edge absorption, X-Ray emission, Mossbauer, XPS, NMR, and various time-resolved pump-probe techniques. The interpretation of spectra is a complicated process, and is currently often based on matching similarities to known spectra, and the use of simple models. The interpretation of the spectra, and perhaps even more importantly, the (structural) characterization of the system implied by the spectroscopy, can be greatly aided by reliable first principles theoretical simulations, the subject of this proposal. In the past we have developed technology to accurately simulate electronic spectroscopy for small molecules. The key ingredients involve the extraction of so-called vibronic model parameters from accurate coupled cluster type electronic structure calculations, and the evolution of quantum nuclear motion on multiple surfaces using non-adiabatic quantum wave packet dynamics. The key challenge is to generalize our methodologies to be applicable to larger systems. We plan to incorporate our methodology in the state-of-the-art ORCA electronic structure program, developed in the group of Frank Neese at MPI Mulheim an der Ruhr, and to capitalize on local correlation, in particular pair natural orbital techniques, which have been applied to systems as large as 50-100 atoms. In addition ORCA allows us to conveniently incorporate relativistic effects, in particular spin-orbit coupling, and this is a vital ingredient to simulate important spectroscopic properties. ORCA will be generalized to compute vibronic model parameters, while simulation of non-adiabatic dynamics is pursued employing the widely used Multiconfiguration Time-Dependent Hartree (MCTDH) package, developed in the Meyer group in Heidelberg, Germany.