Thermochemistry of key soot formation intermediates: C3H3 isomers.
Thermochemistry of key soot formation intermediates: C3H3 isomers.
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DOI：
10.1021/jp0684630
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发表时间：
2007-04
期刊：
影响因子：
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通讯作者：
Steven E. Wheeler;K. Robertson;W. D. Allen;H. Schaefer;Y. Bomble;J. Stanton
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文献类型：
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作者：
Steven E. Wheeler;K. Robertson;W. D. Allen;H. Schaefer;Y. Bomble;J. Stanton
通过从头算能量的系统焦点外推，确定了碳烟形成机理中所涉及的丙二烯、丙炔和四种C3 H3异构体的准确标准生成量。辅助修正已被应用于非谐零点振动能，核心电子相关，对角波恩-奥本海默修正（DBOC），和标量相对论效应。电子关联已经通过二阶Z平均微扰理论（ZAPT 2）和主要通过耦合团簇理论（包括单、双和三重激发，以及对连接的四重激发的微扰处理[ROCCSD，ROCCSD（T），ROCCSDT和UCCSDT（Q）]来解释。采用相关一致的基组层次cc-pVXZ（X = D，T，Q，5，6）。CCSDT（Q）校正不超过0.12千卡摩尔（-）1的相对能量的系统考虑在这里，表明在本结果的电子相关收敛程度高。我们建议的地层压力值如下：Delta（f）H（o）（0）（炔丙基）= 84.76，Delta（f）H（o）（0）（1-丙炔基）= 126.60，Δ（f）H（o）（0）（环丙-1-烯基）= 126.28，δ（f）H（o）（0）（环丙-2-烯基）= 117.36，Δ（f）H（o）（0）（丙二烯）= 47.41，和Δ（f）H（o）（0）（丙炔）= 46.33 kcal mol（-1），估算误差不大于0.3千卡·摩尔~（-1）。相应的C3 H3异构化能比以前的耦合团簇结果大约1 kcal mol（-1），比以前用密度泛函理论得到的结果低几kcal mol（-1）。
Accurate standard enthalpies of formation for allene, propyne, and four C3H3 isomers involved in soot formation mechanisms have been determined through systematic focal point extrapolations of ab initio energies. Auxiliary corrections have been applied for anharmonic zero-point vibrational energy, core electron correlation, the diagonal Born-Oppenheimer correction (DBOC), and scalar relativistic effects. Electron correlation has been accounted for via second-order Z-averaged perturbation theory (ZAPT2) and primarily through coupled-cluster theory, including single, double, and triple excitations, as well as a perturbative treatment of connected quadruple excitations [ROCCSD, ROCCSD(T), ROCCSDT, and UCCSDT(Q)]. The correlation-consistent hierarchy of basis sets, cc-pVXZ (X = D, T, Q, 5, 6), was employed. The CCSDT(Q) corrections do not exceed 0.12 kcal mol(-)1 for the relative energies of the systems considered here, indicating a high degree of electron correlation convergence in the present results. Our recommended values for the enthalpies of formation are as follows: Delta(f)H(o)(0)(propargyl) = 84.76, Delta(f)H(o)(0) (1-propynyl) = 126.60, Delta(f)H(o)(0) (cycloprop-1-enyl) = 126.28, Delta(f)H(o)(0)(cycloprop-2-enyl) = 117.36, Delta(f)H(o)(0)(allene) = 47.41, and Delta(f)H(o)(0)(propyne) = 46.33 kcal mol(-1), with estimated errors no larger than 0.3 kcal mol(-1). The corresponding C3H3 isomerization energies are about 1 kcal mol(-1) larger than previous coupled-cluster results and several kcal mol(-1) below those previously obtained using density functional theory.