论文标题
来自基于神经网络的势能表面的动力学模拟的乙醛与大气过程相关的异构化和分解反应
Isomerization and Decomposition Reactions of Acetaldehyde Relevant to Atmospheric Processes from Dynamics Simulations on Neural Network-Based Potential Energy Surfaces
论文作者
论文摘要
乙醛（AA）异构化（乙烯基醇，VA）和分解（进入CO+CH $ _4 $和H $ _2 $ _2 $+H $ _2 $ CCO）使用完全尺寸的，反应性的电势表面表示为神经网络（NN）。在MP2/Aug-CC-PVTZ计算的432'399参考结构上训练的NN的MAE为0.0453 kcal/mol，RMSE为27'399结构的测试集为1.186 kcal/mol。对于异构化过程，最小动力学路径意味着C-C-C-H（H为h-atom的传递H原子）和C-C-O角度涉及68.2 kcal/mol屏障。使用93.6 kcal/mol的过量能量 - 太阳光谱中可用的能量，足以激发到第一个电子激发态 - 初始化分子动力学，在500 ns时间尺度上未观察到与VA的异构化。仅具有$ \ sim $ 127.6 kcal/mol（包括AA分子的零点能量）的过量能量，同组发生在纳米秒时尺度上。鉴于在平流层中大气条件下的碰撞消极作用发生在100 ns的时间尺度上，因此得出的结论是，在光激发AA后，从光化光子中的va形成不太可能是不可能的。这也将该反应途径的相关性限制为甲酸的来源。
Acetaldehyde (AA) isomerization (to vinylalcohol, VA) and decomposition (into either CO+CH$_4$ and H$_2$+H$_2$CCO) is studied using a fully dimensional, reactive potential energy surface represented as a neural network (NN). The NN, trained on 432'399 reference structures from MP2/aug-cc-pVTZ calculations has a MAE of 0.0453 kcal/mol and an RMSE of 1.186 kcal/mol for a test set of 27'399 structures. For the isomerization process AA $\rightarrow$ VA the minimum dynamical path implies that the C-H vibration, and the C-C-H (with H being the transferring H-atom) and the C-C-O angles are involved to surmount the 68.2 kcal/mol barrier. Using an excess energy of 93.6 kcal/mol - the energy available in the solar spectrum and sufficient to excite to the first electronically excited state - to initialize the molecular dynamics, no isomerization to VA is observed on the 500 ns time scale. Only with excess energies of $\sim$ 127.6 kcal/mol (including the zero point energy of the AA molecule), isomerization occurs on the nanosecond time scale. Given that collisional de-excitation at atmospheric conditions in the stratosphere occurs on the 100 ns time scale, it is concluded that formation of VA following photoexcitation of AA from actinic photons is unlikely. This also limits the relevance of this reaction pathway to be a source for formic acid.
