Intramolecular dynamics diffusion theory approach to complex unimolecular reactions
Intramolecular dynamics diffusion theory approach to complex unimolecular reactions
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DOI：
10.1063/1.478449
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发表时间：
1999-03-22
影响因子：
4.4
通讯作者：
Thompson, DL
中科院分区：
文献类型：
--
作者：
Guo, Y;Shalashilin, DV;Thompson, DL
描述了分子内动力学扩散理论（IDDT）[J. Chem. Phys. 107，6204（1997）]的进一步发展，用于计算IRR控制范围内的单分子反应速率常数。该方法基于Kramers的能量扩散理论，以反应坐标为子系统，其余振动模式为浴。该方法提供了一种实用的手段，获得的速率常数在IVR控制的制度在相当大的节省计算机时间相比，通常的经典轨迹模拟。它的准确性已经在我们早期对一些简单的键裂变反应的应用中得到了证明。在这里描述的研究中，内禀反应坐标（IRC）的想法是用来扩展的IDDT方法更复杂的系统，简单的反应坐标是不容易识别。其基本思想是以IRC为子系统，以横振模为槽。将该方法应用于RDX（hexahydro-1，3，5-trinitro-1，3，5-triazine）的单分子解离，在较宽的能量范围内，用IDDT计算的速率常数与经典轨道模拟结果吻合较好，表明该方法可普遍适用于大型多原子体系. (C)1999年美国物理学会。[S0021-9606（99）01711-0]。
A further development of the intramolecular dynamics diffusion theory (IDDT) [J. Chem. Phys. 107, 6204 (1997)] for computing unimolecular reaction rate constants in the IVR-controlled regime is described. The approach is based on Kramers' energy diffusion theory, with the reaction coordinate taken as the subsystem and the rest of the vibrational modes as the bath. The method provides a practical means of obtaining the rate constants in the IVR-controlled regime at considerable savings of computer time compared to the usual classical trajectory simulations. Its accuracy has been demonstrated in our earlier applications to some simple bond-fission reactions. In the study described here the idea of intrinsic reaction coordinate (IRC) is used to extend the IDDT approach to more complicated systems for which simple reaction coordinates are not easily identifiable. The basic idea is to take the IRC as the subsystem and the transverse vibrational modes as the bath. The method is applied to the unimolecular dissociation of RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), and the rate constants calculated using IDDT are in good agreement with classical trajectory simulations over a wide range of energies, suggesting that the approach may be generally applicable to large polyatomic systems. (C) 1999 American Institute of Physics. [S0021-9606(99)01711-0].