Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
J Chem Phys. 2012 Dec 14;137(22):224103. doi: 10.1063/1.4769079.
We investigate on the procedure of extracting a "spectral density" from mixed QM/MM calculations and employing it in open quantum systems models. In particular, we study the connection between the energy gap correlation function extracted from ground state QM/MM and the bath spectral density used as input in open quantum system approaches. We introduce a simple model which can give intuition on when the ground state QM/MM propagation will give the correct energy gap. We also discuss the role of higher order correlators of the energy-gap fluctuations which can provide useful information on the bath. Further, various semiclassical corrections to the spectral density, are applied and investigated. Finally, we apply our considerations to the photosynthetic Fenna-Matthews-Olson complex. For this system, our results suggest the use of the Harmonic prefactor for the spectral density rather than the Standard one, which was employed in the simulations of the system carried out to date.
我们研究了从混合 QM/MM 计算中提取“谱密度”并将其应用于开放量子系统模型的方法。具体来说，我们研究了从基态 QM/MM 中提取的能隙相关函数与作为开放量子系统方法输入的浴谱密度之间的关系。我们引入了一个简单的模型，该模型可以提供直觉，说明何时基态 QM/MM 传播将给出正确的能隙。我们还讨论了能隙波动的更高阶相关函数的作用，这些相关函数可以提供有关浴的有用信息。此外，还应用和研究了各种半经典谱密度校正。最后，我们将我们的考虑应用于光合作用的 Fenna-Matthews-Olson 复合物。对于该系统，我们的结果表明，与迄今为止用于该系统模拟的标准谱密度相比，应使用谐波前因子。
