Methyl radical: ab initio global potential surface, vibrational levels and partition function
Methyl radical: ab initio global potential surface, vibrational levels and partition function
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甲基自由基：从头算全局势面、振动能级和配分函数
DOI：
10.1080/00268970500238663
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发表时间：
2006
影响因子：
1.7
通讯作者：
Stephen K. Gray *
中科院分区：
文献类型：
--
作者：
D. Medvedev;L. B. Harding;Stephen K. Gray *
在CH3体系上进行了高层多参考、组态交互计算。基于这些结果，建立了一个能够描述H2 + CH（2Π）→H + CH2（3B1）反应的解析性全局势能面。利用这个表面和核运动的Jacobi坐标表示，Lanczos方法被用来计算甲基自由基CH3（）的最低振动态。三态亚甲基CH2（3B1）的最低能级也得到了。与ν2离面伞形运动激发有关的CH3能级表现出强烈的四次非调和效应，这与先前的实验和理论结果一致。基于伞型和面内对称C-H拉伸（ν1）模态耦合的二维模型解释了ν2能级模式。评估了非调和性对振动配分函数的影响。
High-level multi-reference, configuration interaction calculations are performed on the CH3 system. Based on these results, an analytical, global potential energy surface capable of describing the H2 + CH(2Π) → H + CH2( 3B1) reaction is developed. Employing this surface, and a Jacobi coordinates representation of the nuclear motion, the Lanczos method is used to calculate the lowest vibrational states of the methyl radical, CH3( ). The lowest energy levels of the triplet methylene, CH2( 3B1), are also obtained. The CH3 levels associated with excitation of the ν2 out-of-plane umbrella motion display a strong quartic anharmonicity effect, in agreement with earlier experimental and theoretical results. A two-dimensional model based on coupling the umbrella and in-plane symmetric C–H stretch (ν1) modes accounts for the ν2 level patterns. The impact of anharmonicity on the vibrational partition function is assessed.