AB INITIO CALCULATIONS OF VITAMIN B12 COMPOUNDS

这个子项目是许多研究子项目中的一个 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。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 我们正在开发的拉曼频率和强度的计算银簇分子系统和取代钴胺素分子的振动耦合是重要的。我们还计算了取代钴胺素分子的电子光谱和键断裂过程。我们的计划是首先使用量子化学程序的高斯或ADF包计算钴胺素分子和银簇分子系统的优化基态（DFT）和激发态（TD-DFT），并计算它们的简正模坐标和频率。我们将在B3 LYP混合泛函水平上使用LANL 2DZ双zeta基组和/或具有非局部相关性的BP 86泛函和TZVP基组。模式的相对活性将与相对实验强度结果进行比较。我们将计算和比较静态和动态极化率。然后，我们将计算共振拉曼强度使用ADF或道尔顿量子化学程序，采取数值导数的动态极化率张量分量相对于正常模式位移。对于金属簇（纳米颗粒）和取代钴的分子，我们将计算激发态势能面，偶极跃迁矩和振子强度。最后通过计算电子耦合常数来研究振动耦合的影响。

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 are developing computations of Raman frequencies and intensities for Ag-cluster-molecule systems and for substituted-cobalamin molecules where vibronic coupling is important. Also we are calculating electronic spectra and bond breaking processes in the substituted-cobalamin molecules. Our plan is to first calculated optimized ground states ( DFT) and excited states (TD-DFT) of cobalamin molecules and the Ag-cluster-molecule systems and to calculate their normal mode coordinates and frequencies, using the Gaussian or ADF package of quantum chemistry programs. We will use the LANL2DZ double zeta basis set at the B3LYP hybrid functional level and/or the BP86 functional with nonlocal correlation and the TZVP basis set. Relative activity of the modes will be compared to relative experimental intensity results. We will calculate and compare both static and dynamic polarizabilities. Then we will calculate resonant Raman intensities using either the ADF or the Dalton quantum chemistry program by taking numerical derivatives of the dynamic polarizability tensor components with respect to the normal mode displacements. For molecules on metal-clusters (nanoparticles) and for substituted-cobalamins, we will calculate excited state potential energy surfaces , dipole transition moments, and oscillator strengths. Finally the effect of vibonic coupling will be investigated by calculating the electronic coupling constants.