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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Electrostatic DFT Map for the Complete Vibrational Amide Band of NMA
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Electrostatic DFT Map for the Complete Vibrational Amide Band of NMA

机译：NMA的完整振动酰胺带的静电DFT图

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摘要

An anharmonic vibrational Hamiltonian for the amide I,II,III,and A modes of N-methyl acetamide(NMA),recast in terms of the 19 components of an external electric field and its first and second derivative tensors(electrostatic DFT map),is calculated at the DFT(BPW91/6-31G(d,p))level.Strong correlations are found between NMA geometry and the amide frequency fluctuations calculated using this Hamiltonian together with the fluctuating solvent electric field obtained from the MD simulations in TIP3 water.The amide I and A frequencies are strongly positively correlated with the C=O and N-H bond lengths.The C=O and C-N amide bond lengths are negatively correlated,suggesting the solvent-induced fluctuations of the contribution of zwitterionic resonance form.Sampling the global electric field in the entire region of the transition charge densities(TCDs)is required for accurate infrared line shape simulations.Collective electrostatic solvent coordinates which represent the fluctuations of the 10 lowest amide fundamental and overtone states are reported.Normal-mode analysis of an NMA-3H_2O cluster shows that the 660 cm~(-1)to 1100 cm~(-1)oscillation found in the frequency autocorrelation functions of the amide modes may be ascribed to the two bending vibrations of intermolecular hydrogen bonds with the amide oxygen of NMA.
机译：N-甲基乙酰胺（NMA）的酰胺I，II，III和A模式的非谐振动哈密顿量，根据外部电场的19个分量及其一阶和二阶导数张量（静电DFT映射）重铸，在DFT（BPW91 / 6-31G（d，p））级别上计算得出。发现NMA几何形状与使用该哈密顿量计算的酰胺频率波动以及从TIP3水中的MD模拟获得的波动溶剂电场之间存在强相关性酰胺I和A的频率与C = O和NH键的长度强烈正相关.C = O和CN酰胺键的长度负相关，建议溶剂引起两性离子共振形式贡献的波动。精确的红外线形仿真需要过渡电荷密度（TCD）整个区域中的全局电场。集体静电溶剂坐标表示10个分子的波动NMA-3H_2O团簇的正模分析表明，在酰胺模式的频率自相关函数中发现的660 cm〜（-1）至1100 cm〜（-1）振荡可能是最低的。归因于分子间氢键与NMA酰胺氧的两次弯曲振动。

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