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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Optical Characterization of Chemistry in Shocked Nitromethane with Time-Dependent Density Functional Theory
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Optical Characterization of Chemistry in Shocked Nitromethane with Time-Dependent Density Functional Theory

机译：时变密度泛函理论在震惊硝基甲烷中化学反应的光学表征

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摘要

We compute the optical properties of the liquid-phase energetic material nitromethane (CH_3NO_2) for the first 100 ps behind the front of a simulated shock at 6.5 km/s, close to the experimentally observed detonation shock speed of the material. We utilize molecular dynamics trajectories computed using the multiscale shock technique (MSST) for time-resolved optical spectrum calculations based on both linear response timedependent DFT (TDDFT) and the Kubo?Greenwood formula with Kohn?Sham DFT wave functions. We find that the TDDFT method predicts an optical conductivity 25?35% lower than the Kubo?Greenwood calculation and provides better agreement with the experimentally measured index of refraction of unreacted nitromethane. We investigate the influence of electronic temperature on the Kubo?Greenwood spectra and find no significant effect at optical wavelengths. In both Kubo?Greenwood and TDDFT, the spectra evolve nonmonotonically in time as shock-induced chemistry takes place. We attribute the timeresolved absorption at optical wavelengths to time-dependent populations of molecular decomposition products, including NO, CNO, CNOH, H_2O, and larger molecules. These calculations offer direction for guiding and interpreting ultrafast optical measurements on reactive materials.
机译：我们以6.5 km / s的速度模拟冲击的前100 ps，计算了液相高能材料硝基甲烷（CH_3NO_2）的光学特性，接近该材料的爆炸爆炸冲击速度。我们利用基于线性响应时间相关DFT（TDDFT）和具有Kohn？Sham DFT波函数的Kubo？Greenwood公式的时间分辨光谱计算，利用了使用多尺度冲击技术（MSST）计算的分子动力学轨迹。我们发现，TDDFT方法预测的光导率比Kubo？Greenwood计算的低25％至35％，并且与未反应的硝基甲烷的实验测量折射率提供了更好的一致性。我们研究了电子温度对Kubo？Greenwood光谱的影响，并发现在光波长下没有显着影响。在Kubo？Greenwood和TDDFT中，随着激波诱导的化学反应发生，光谱随时间非单调地演化。我们将光波长下的时间分辨吸收归因于分子分解产物（包括NO，CNO，CNOH，H_2O和更大的分子）的时间依赖性种群。这些计算为指导和解释反应性材料的超快光学测量提供了方向。

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