甲硫醇和氢原子反应的从头算直接动力学.pdf

物理化学学报( Wuli Huaxue Xuebao)
Acta Phy..-Chim.Sin,2010,26(1):183-187
183
Article」
www.whxb.pku.edu.cn
甲硫醇和氢原子反应的从头算直接动力学
王永震段雪梅王钦刘靖尧
(吉林大学理论化学研究所,理论化学计算国家重点实验室,长春130023)
搞要:利用双水平直接动力学方法对反应CHSH+H的微观机理和动力学性质进行了理论研究.对于此反应
的三个反应通道,即-SH和CH3基团上的两个氢提取通道及一个取代通道,在MP/6-311+G(d,P)水平上优化
得到了各稳定点的结构及振动频率,并在G3(MP2)水平上进行了单点能量计算以获得更精确的能量信息;在此
基础上运用结合小曲率隧道效应校正的变分过渡态理论( CVTACT计算了各反应通道在220-1000K温度区间
的速率常数.计算结果表明提取一SH基团上H的反应通道RI在整个反应温度区间都是主要通道,而随着温度
的升高,低温下的次要反成通道一取代通道R3变得越来越重要,并且在高温下将成为一个竞争的反应通道;
提取一CH1基团上H的反应通道(R2)由于具有较髙的反应能全,因而,其对总反应速率常数的贡献可以忽略.计
算得到的总反应速率常数与已有的实验值符合得很好,进而我们预测了该反应在220-1000K温度范围内速率
常数的表达式为:k=500x10Texp(-119.81/,为将来的实验研究提供参考
关键词:直接动力学;从头算;G3MP2);速率常数;变分过渡态理论
中图分类号:0641;:0043
Direct Ab initio Dynamics on the Reaction of Methanethiol and
Hydrogen Atom
WANG Yong-xia DUAN Xue-mei WANG Qin LTU Jing-yao
(State Key Laboratory af Theoretical and Computational Chemistry, institute of Theoretical Chemistry, ilin University,
30023,P.R.
Abstract We studied the reaction of CHSH+H theoretically using a dual-level direct dynamics method. Three
reaction channels two H-abstraction(from the -SH and-ch groups)and one substitution channels, were found
Optimized geometries, frequencies, and energies of the stationary points as well as extra points along the minimum
energy path were calculated at the MP2/6-311+G(d, p)level of theory. The potential energy profiles were then relined
by sing e-point energy calculations at the G(MP2 )level. Furthermore, the rate constants of all three channels were
evaluated by canonical variational transition state thcory(T) with the small-urvature tunneling eftect correction(CT)
over the wide emperature range of 20-1000 K. These calculations show that H-abstraction from the-sh group(R)
is the major channel for the title reaction over the whole temperature range. The substitution channel(R3)is a minor
pathway at low temperatures and becomes more important as the temperature increases. This would bc a competitive
channel at high temperature while the contribution of H-abstraction from the group(R2)to the overall rate constant
is almost negligible because of its high energy barrier. The calculated CVT/SCT rate constants agree well with the
available experimental values. The three-parameter rate-temperature expression for the total reaction over the whole
temperature range of 220-1000 K is shown to be k=5.00x10-exp(-119 81/7), which may be a useful expression
for future experiments
Key Words: Direct dynamics; Ab initio; G3(MP2) Rate constant; Canonical variational transition state
Received: September 25, 2009 Revised: November 9. 2009; Published on Web: December 2, 2009
Correspondingauthor.Email:ljy(@jlu.edu.cn:Tel:+86-431-88498016;Fax:+86-431-88198026
The project was supported by the National Natual Science Foundation of China(20333050, 2030307, 20973077)and Program for New Century
Excellcnt Talents in University, China (NCET)
国家自然科学基金(20833050,20303007,20973077)和教育部新世纪优秀人オ支持计划(NCET资助项目
C Editorial office of Acta Physico-chimica Sinica