Can theory quantitatively model stratospheric photolysis? Ab initio estimate of absolute absorption cross sections of ClOOCl.
Can theory quantitatively model stratospheric photolysis? Ab initio estimate of absolute absorption cross sections of ClOOCl.
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理论可以定量模拟平流层光解作用吗？
DOI：
10.1063/1.3499599
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
P. Slavíček
中科院分区：
文献类型：
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作者：
M. Ončák;Lukáš Šištík;P. Slavíček
计算了过氧化二氯在250-400 nm范围内的吸收光谱。我们采用了五种不同的方法来定量模拟吸收截面（经验加宽方案，线性谐波反射原理和全反射原理与基态密度计算使用谐波近似，经典分子动力学和路径积分分子动力学）。我们还测试了各种单引用和多引用方法。我们发现：（i）ClOOCl的激发特性对分子几何形状敏感，因此必须对基态密度进行适当采样;（ii）单参考方法往往会高估吸收截面，导致吸收最大值发生蓝移。在CASPT 2水平上，采用完全主动空间组态相互作用（CAS-SCF）跃迁偶极矩，结合路径积分分子动力学方法对基态进行采样，计算得到的吸收光谱与实验符合较好.然而，我们没有在与大气相关的低能量光谱尾部达成完全一致。一般的信息是，定量预测是困难的，即使是一个相对较小的分子ClOOCl和收敛，相对于电子结构的方法，所使用的基组，和基态采样，需要仔细检查。
We have calculated the absorption spectrum of dichlorine peroxide (ClOOCl) in the spectral range 250-400 nm. We have employed five different approaches to quantitatively model the absorption cross section (empirical broadening scheme, linearized harmonic reflection principle and full reflection principle with ground state density calculated using harmonic approximation, classical molecular dynamics, and path-integral molecular dynamics). We have also tested various single and multireference methods. We found that (i) the excitation characteristics of ClOOCl are sensitive on molecular geometries and therefore the ground state density has to be properly sampled and that (ii) single-reference methods tend to overestimate the absorption cross section and lead to a blueshift in the absorption maximum. The absorption spectrum calculated at the CASPT2 level with complete active space-configuration interaction (CAS-SCF) transition dipole moment with the ground state sampled via path-integral molecular dynamics is in a good agreement with the experiment. We, however, did not reach full agreement in the atmospherically relevant low-energy tail of the spectrum. The general message is that quantitative predictions are difficult even for a relatively small molecule as ClOOCl and the convergence, with respect to the electronic structure method, basis set used, and ground state sampling, needs to be carefully examined.