Kiewisch Karin, Neugebauer Johannes, Reiher Markus
Laboratorium fur Physikalische Chemie, ETH Zurich, Zurich, Switzerland.
J Chem Phys. 2008 Nov 28;129(20):204103. doi: 10.1063/1.3013351.
We present an intensity-driven approach for the selective calculation of vibrational modes in molecular resonance Raman spectra. The method exploits the ideas of the mode-tracking algorithm [M. Reiher and J. Neugebauer, J. Chem. Phys. 118, 1634 (2003)] for the calculation of preselected molecular vibrations and of Heller's gradient approximation [Heller et al., J. Phys. Chem. 86, 1822 (1982)] for the estimation of resonance Raman intensities. The gradient approximation allows us to construct a basis vector for the subspace iteration carried out in the mode-tracking calculation, which corresponds to an artificial collective motion of the molecule that contains the entire intensity in the resonance Raman spectrum. Subsequently, the algorithm generates new basis vectors from which normal mode approximations are obtained. It is then possible to provide estimates for (i) the accuracy of the normal mode approximations and (ii) the intensity of these modes in the final resonance Raman spectrum. This approach is tested for the examples of uracil and a structural motif from the E colicin binding immunity protein Im7, in which a few aromatic amino acids dominate the resonance Raman spectrum at wavelengths larger than 240 nm.
我们提出了一种强度驱动的方法，用于选择性计算分子共振拉曼光谱中的振动模式。该方法利用了模式跟踪算法[M. 赖尔和J. 诺伊格鲍尔，《化学物理杂志》118, 1634 (2003)]的思想来计算预选的分子振动，并利用了海勒的梯度近似[海勒等人，《物理化学杂志》86, 1822 (1982)]来估计共振拉曼强度。梯度近似使我们能够为模式跟踪计算中进行的子空间迭代构建一个基向量，该基向量对应于分子的一种人工集体运动，其包含共振拉曼光谱中的全部强度。随后，该算法生成新的基向量，并从中获得简正模式近似。进而能够提供关于(i)简正模式近似的准确性和(ii)这些模式在最终共振拉曼光谱中的强度的估计。以尿嘧啶以及大肠杆菌素结合免疫蛋白Im7中的一个结构基序为例对该方法进行了测试，在该结构基序中，一些芳香族氨基酸在波长大于240 nm时主导共振拉曼光谱。
