AB INITIO CALCULATIONS OF VITAMIN B12 COMPOUNDS

维生素 B12 化合物的从头计算

• 批准号: 7601330
• 负责人: RONALD L BIRKE
• 金额: $ 0.03万
• 依托单位: CARNEGIE-MELLON UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-08-01 至 2008-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7601330
• 关键词: 3-hydroxyflavone; Cobalamin; Computer Retrieval of Information on Scientific Projects Database; Coupled; Equation; Equilibrium; Frequencies; Funding; Grant; Institution; Lead; Methods; Molecular; Property; Raman Spectrum Analysis; Relative (related person); Research; Research Personnel; Resources; Solutions; Source; Surface; United States National Institutes of Health; Vitamin B 12; programs; pyridine; quantum chemistry

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We would like to calculate properties of open-shell vitamin B12 (cobalamin) molecules and the intensities of the Raman spectroscopy for molecules on surfaces. In both cases a break down in the Born-Oppenheimer approximation can lead to vibronic interactions which distorts the molecular geometry ( PJT effect) for cobalamins or changes the relative Raman intensities for molecules on surfaces. We will calculate the properties of cobalamin molecules using the CASSCF method ; however , we will be investing other possible approaches using TD-DFT where the computation is more efficient. We will calculate Raman intensities by an ab initio method which should include both Franck-Condon and Herzberg-Teller type resonance Raman scattering. This approach will be used in order to obtain an understanding of the basic enhancement mechanisms of Surface Enhanced Raman Scattering (SERS). This calculation will be made for pyridine and 3-hydroxyflavone compounds on a Ag nanocluster. One possible calculation method involves using the Gaussian package of programs for solutions to the coupled perturbed Hartree-Fock equations ( CPHF) for multiconfigurational CASSCF wave functions in order to obtain the frequency-dependent polarizability components. The Raman scattering intensities are then found from the differential scattering cross section by evaluating numerical derivatives of the dynamic polarizability as a function of Cartesian displacements of all atoms with respect to the equilibrium geometry. Other approaches to this calculation will be investigated in the ADF or MOLPRO packages for quantum chemistry.

这个子项目是许多利用 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。列出的机构为 中心，但不一定是研究者所在的机构。 我们想计算开壳维生素B12（钴胺素）分子的性质和表面分子的拉曼光谱的强度。在这两种情况下，在玻恩-奥本海默近似的故障可能会导致振动相互作用，扭曲的钴的分子几何形状（PJT效应）或改变表面上的分子的相对拉曼强度。我们将使用CASSCF方法计算钴胺素分子的性质;然而，我们将使用TD-DFT研究其他可能的方法，其中计算更有效。我们将通过从头计算方法计算拉曼强度，该方法应包括Franck-Condon和Herzberg-Teller型共振拉曼散射。这种方法将被用来获得的基本增强机制的表面增强拉曼散射（Sers）的理解。该计算将针对Ag纳米团簇上的吡啶和3-羟基黄酮化合物进行。一种可能的计算方法涉及使用高斯包的程序的解决方案的耦合微扰Hartree-Fock方程（CPHF）的多组态CASSCF波函数，以获得频率相关的极化率组件。的拉曼散射强度，然后发现从微分散射截面通过评估作为笛卡尔位移的所有原子相对于平衡几何形状的函数的动态极化率的数值导数。这种计算的其他方法将在量子化学的ADF或MOLPRO软件包中进行研究。