Quantum Theory Project, Department of Chemistry and Physics, University of Florida, Gainesville, Florida 32611, USA.
Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, USA.
J Chem Phys. 2019 Feb 28;150(8):084105. doi: 10.1063/1.5081827.
A combined (fixed-J) two-dimensional master-equation/semi-classical transition state theory/variational Rice-Ramsperger-Kassel-Marcus approach has been used to compute reaction rate coefficients of OH with CHOH over a wide range of temperatures (10-2500 K) and pressures (10-10 Torr) based on a potential energy surface that has been constructed using a modification of the high accuracy extrapolated ab initio thermochemistry (HEAT) protocol. The calculated results show that the title reaction is nearly pressure-independent when T > 250 K but depends strongly on pressure at lower temperatures. In addition, the preferred mechanism and rate constants are found to be very sensitive to temperature. The reaction pathway CHOH + OH → CHO + HO proceeds exclusively through tunneling at exceedingly low temperatures (T ≤ 50 K), typical of those established in interstellar environments. In this regime, the rate constant is found to increase with decreasing temperature, which agrees with low-temperature experimental results. The thermodynamically favored reaction pathway CHOH + OH → CHOH + HO becomes dominant at higher temperatures (T ≥ 200 K), such as those found in Earth's atmosphere as well as combustion environments. By adjusting the ab initio barrier heights slightly, experimental rate constants from 200 to 1250 K can be satisfactorily reproduced.
一种结合（固定-J）二维主方程/半经典过渡态理论/变分 Rice-Ramsperger-Kassel-Marcus 方法已被用于根据使用改进的高精度外推从头算热化学 (HEAT) 协议构建的势能面，计算在很宽的温度（10-2500 K）和压力（10-10 托）范围内 OH 与 CHOH 的反应速率系数。计算结果表明，当 T > 250 K 时，标题反应几乎与压力无关，但在较低温度下强烈依赖于压力。此外，发现首选机制和速率常数对温度非常敏感。反应途径 CHOH + OH → CHO + HO 通过隧穿仅在极低温度（T ≤ 50 K）下进行，这与星际环境中建立的温度典型值一致。在该区域中，发现速率常数随温度降低而增加，这与低温实验结果一致。在更高的温度（T ≥ 200 K）下，热力学上有利的反应途径 CHOH + OH → CHOH + HO 变得占主导地位，例如在地球大气以及燃烧环境中发现的温度。通过稍微调整从头算势垒高度，可以令人满意地再现 200 到 1250 K 的实验速率常数。
