A full-dimensional coupled-surface study of the photodissociation dynamics of ammonia using the multiconfiguration time-dependent Hartree method.
A full-dimensional coupled-surface study of the photodissociation dynamics of ammonia using the multiconfiguration time-dependent Hartree method.
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DOI：
10.1063/1.3614038
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发表时间：
2011-07
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影响因子：
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通讯作者：
K. Giri;Emma Chapman;C. Sanz;G. Worth
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文献类型：
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作者：
K. Giri;Emma Chapman;C. Sanz;G. Worth
利用最近发展起来的耦合从头算势能面（PESs），利用多构型时变Hartree （MCTDH）方法对Ã态NH(3)和ND(3)的光解动力学进行了全维量子力学计算。李H.， R. Valero， D. G. Truhlar，理论。詹。法典118,9(2007)]。为了有效地使用MCTDH方法，将PESs表示为基于高维模型表示。计算了两种同位素体在基电子态的第零振动态下的Ã←X→吸收光谱。为了处理较大的系统，使用雅可比坐标。对二维、三维、五维和六维模型系统进行了耦合PES计算，以了解降维计算的有效性。除了完全耦合计算外，非绝热耦合对吸收光谱的影响通过仅在Ã电子状态下传播初始波包来显示。计算得到的吸收光谱与现有的理论和实验观测结果一致。与使用拉道坐标和价坐标的计算比较，表明了明确地包括系统对称性的效果。最后，计算了两个通道中氢原子损失的分支比。这些结果预示了非绝热积随计算量纲的增大而增大，并证实了全量纲计算的重要性。
Full-dimensional quantum mechanical computations are carried out to investigate the photodissociation dynamics of à state NH(3) and ND(3) using the multiconfiguration time-dependent Hartree (MCTDH) method with recently developed coupled ab initio potential energy surfaces (PESs) [Z. H. Li, R. Valero, and D. G. Truhlar, Theor. Chim. Acc. 118, 9 (2007)]. To use the MCTDH method efficiently the PESs are represented as based on the high-dimensional model representation. The à ← X̃ absorption spectra for both isotopomers were calculated for the zeroth vibrational state of the ground electronic state. With a view to treating larger systems, Jacobi coordinates are used. Computations on the coupled PES are carried out for two-, three-, five-, and six-dimensional model systems to understand the validity of reduced-dimensional calculations. In addition to the fully coupled calculations, the effect of nonadiabatic coupling on absorption spectra is shown by propagating the initial wavepacket only in the à electronic state. The calculated absorption spectra are shown to be in good agreement with available theoretical and experimental observations. Comparisons with calculations using Radau and valence coordinates show the effect of including the symmetry of the system explicitly. Finally, branching ratios for loss of a hydrogen atom via the two available channels are calculated. These predict that the nonadiabatic product increases with the dimension of the calculations and confirm the importance of the full-dimensional calculations.