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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Application of Multipolar Charge Models and Molecular Dynamics Simulations to Study Stark Shifts in Inhomogeneous Electric Fields
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Application of Multipolar Charge Models and Molecular Dynamics Simulations to Study Stark Shifts in Inhomogeneous Electric Fields

机译：应用多极电荷模型和分子动力学模拟研究非均匀电场中的斯塔克位移

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摘要

Atomic multipole moments are used to investigate vibrational frequency shifts of CO and H2 in uniform and inhomogeneous electric fields using ab initio calculations and Molecular Dynamics (MD) simulations. The importance of using atomic multipole moments that can accurately represent both molecular electrostatics and the vibrational response of the molecule to changes in the local electric field is highlighted. The vibrational response of CO to applied uniform and inhomogeneous electric fields is examined using Density Functional Theory calculations for a range of test fields, and the results are used to assess the performance of different atomic multipole models. In uniform fields, the calculated Stark tuning rates of Δμ ) 0.52 cm-1/ (MV/cm) (DFT), Δμ ) 0.55 cm-1/(MV/cm) (fluctuating three-point charge model), and Δμ ) 0.64 cm-1/ (MV/cm) (Multipole model up to octupole), compare favorably with the experimentally measured value of 0.67 cm-1/(MV/cm). For H2, which has no permanent dipole moment, CCSD(T) calculations demonstrate the importance of bond-weakening effects in force fields in response to the applied inhomogeneous electric field. Finally, CO in hexagonal ice is considered as a test system to highlight the performance of selected multipolar models in MD simulations. The approach discussed here can be applied to calibrate a range of multipolar charge models for diatomic probes, with applications to interpret Stark spectroscopy measurements in protein active sites.
机译：多原子矩用于通过从头算和分子动力学（MD）模拟研究均匀电场和非均匀电场中CO和H2的振动频移。强调了使用原子多极矩来精确表示分子静电以及分子对局部电场变化的振动响应的重要性。使用密度泛函理论计算了一系列测试场，研究了CO对施加的均匀电场和非均匀电场的振动响应，并将结果用于评估不同原子多极模型的性能。在均匀场中，计算出的Stark调谐速率为Δμ）0.52 cm-1 /（MV / cm）（DFT），Δμ）0.55 cm-1 /（MV / cm）（波动三点电荷模型）和Δμ） 0.64 cm-1 /（MV / cm）（直到八极的多极模型），与实验测量值0.67 cm-1 /（MV / cm）相比具有优势。对于没有永久偶极矩的H2，CCSD（T）计算证明了响应于施加的非均匀电场，力场中键弱化效应的重要性。最后，六角形冰中的一氧化碳被认为是测试系统，以突出MD模拟中所选多极模型的性能。本文讨论的方法可用于校准双原子探针的一系列多极电荷模型，并用于解释蛋白质活性位点的Stark光谱测量。

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