Zero-point energy constraints in RRKM end non-RRKM molecules
Zero-point energy constraints in RRKM end non-RRKM molecules
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DOI：
10.1039/a808024k
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发表时间：
1999-01-01
影响因子：
3.3
通讯作者：
Lim, KF
中科院分区：
文献类型：
--
作者：
McCormack, DA;Lim, KF
用于零点能量（ZPE）保存的TRAPZ方法（Lim和McCormack，J. Chem. Phys.，1995，102，1705）被推广到非零角动量的分子系统。该方法被证明是守恒的线动量，角动量和总能量。它也被发现保持固有的水稻Ramsperger-Kassel-Marcus（RRKM）行为的解离Al-3集群。TRAPZ速率系数低于经典系综的计算值，因为相空间中具有小于ZPE的区域不能再反应。根据需要，RRKM速率系数是TRAPZ速率系数的上限。由于瞬时正常模式ZPE的波动，TRAPZ反应阈值高于经典（渐近极限）产品ZPE。当Al-3 ZPE弯曲运动转化为Al-2角动量时，产生旋转热Al-2。TRAPZ方法不保留HNC异构化的非RRKM行为。
The TRAPZ method for zero-point energy (ZPE) preservation (Lim and McCormack, J. Chem. Phys., 1995, 102, 1705) is generalised to molecular systems of non-zero angular momentum. The method is shown to conserve linear momentum, angular momentum and total energy. It is also found to preserve the intrinsic Rice-Ramsperger-Kassel-Marcus (RRKM) behaviour of a dissociating Al-3 cluster. The TRAPZ rate coefficients are lower than those calculated for classical ensembles, since regions of phase space with less than ZPE can no longer react. As required, the RRKM rate coefficients are upper bounds to the TRAPZ rate coefficients. The TRAPZ reaction threshold is higher than the classical (asymptotic-limit) product ZPE due to fluctuations in instantaneous normal mode ZPEs. Rotationally hot Al-2 is produced as Al-3 ZPE bending motion is converted to Al-2 angular momentum. The TRAPZ method does not preserve the non-RRKM behaviour of HNC isomerisation.