偏二甲肼分解及NO_(2)脱氢反应速率常数计算  

Calculation of Rate Coefficients for Unsymmetrical Dimethylhydrazine Decomposition and NO_(2)Abstraction Reactions

作　　者：殷阁媛 尤佳俊 胡二江[1] 黄佐华[1] YIN Geyuan;YOU Jiajun;HU Erjiang;HUANG Zuohua(State Key Laboratory of Multiphase Flow in Power Engineering,Xi’an Jiaotong University,Xi’an 710049,China)

机构地区：[1]西安交通大学动力工程多相流国家重点实验室,西安710049

出　　处：《西安交通大学学报》2024年第12期208-216,共9页Journal of Xi'an Jiaotong University

基　　金：国家自然科学基金资助项目(52106182);先进航空动力创新工作站资助项目(HKCX2024-01-022)。

摘　　要：针对偏二甲肼与N_(2)O_(4)化学反应动力学模型的不准确问题,开展了关键反应的高精度量子化学计算。首先,基于从头算方法,开展了偏二甲肼单分子分解及NO_(2)脱氢反应速率常数计算,利用CCSD(T)/cc-pVTZ//B2PLYPD3/6-311++G(d,p)计算级别得到反应体系的势能面;接着,采用多参考态方法和CASPT2/CBS//CASPT2/cc-pVTZ计算级别,修正了无势垒反应的势能面;最后,通过气相单分子反应理论/主方程理论求解温度和压力相关的速率常数,采用变分过渡态理论求解无势垒反应的速率常数。数值结果表明:计算得到的速率常数与实验结果吻合良好,得到的生成焓与活性热化学表及NIST数据库的结果相差不超过4.18 kJ·mol^(-1),熵相差不超过2.09 J·K^(-1)·mol^(-1);偏二甲肼分解的主要反应通道为CH_(3)+CH_(3)NNH_(2)及NH_(2)+CH_(3)NCH_(3),NO_(2)脱氢的关键反应通道为CH_(3)(CH_(2))NNH_(2)+HONO;对于低势垒和无势垒反应,相较于传统过渡态理论,变分过渡态理论能够更准确地计算出所有速率常数,并同时给出其在不同压力和温度下的不确定度。研究结果可为火箭发动机燃烧室的数值模拟提供理论支撑。To address the issue of inaccuracies in the kinetic model of the chemical reactions between unsymmetrical dimethylhydrazine and N_(2)O_(4),high-precision quantum chemical calculations of key reactions are conducted.Initially,employing ab initio methods,the rate coefficients for unsymmetrical dimethylhydrazine decomposition and NO_(2)abstraction reactions are computed.The potential energy surface of the reaction system is determined using the CCSD(T)/cc-pVTZ//B2PLYPD3/6-311++G(d,p)calculation level.Subsequently,the potential energy surface of barrierless reactions is corrected utilizing the multi-reference state method and the CASPT2/CBS//CASPT2/cc-pVTZ calculation level.Finally,temperature and pressure-dependent rate coefficients are obtained employing gas-phase unimolecular reaction theory/master equation theory,and rate coefficients for barrierless reactions are calculated using variational transition state theory.The numerical results demonstrate that the calculated rate coefficients are well aligned with experimental results,with differences in enthalpy of formation not exceeding 4.18 kJ·mol^(-1)when compared to data from active thermochemical tables and the NIST database,and entropy differences within 2.09 J·K^(-1)·mol^(-1).The primary routes for unsymmetrical dimethylhydrazine decomposition involve the generation of CH_(3)+CH_(3)NNH_(2)and NH_(2)+CH_(3)NCH_(3).In the NO_(2)dehydrogenation reaction,the pathway leading to CH_(3)(CH_(2))NNH_(2)+HONO exhibits the highest proportion.Variational transition state theory proves to be more precise in calculating rate coefficients for reactions with low or no barriers than traditional transition state theory,also providing uncertainties across various pressures and temperatures.These research outcomes can provide essential theoretical backing for numerical simulations of rocket engine combustion chambers.

关 键 词：量子化学计算 偏二甲肼 速率常数 主方程理论 

分 类 号：V231.21[航空宇航科学与技术—航空宇航推进理论与工程]