X-ray Emission Spectroscopy of Nitrogen-Rich Compounds

Nonresonant X-ray emission spectroscopy was used to compare the nitrogen-rich compounds ammonium nitrate, trinitrotoluene, and cyclotrimethylene−trinitramine. They are representative of crystalline and molecular structures of special importance in industrial and military applications. The spectral signature of each substance was analyzed and correlated with features in the electronic structure of the systems. This analysis was accomplished by means of theoretical simulations of the emission spectra and a detailed examination of the molecular orbitals and densities of states. We find that the two theoretical methods used (frozen-orbital density functional theory and real-space Green’s function simulations) account semiquantitatively for the observed spectra and are able to predict features arising from distinct chemical complexes. A comparison of the calculations and the data provides insight into the electronic contributions of specific molecular orbitals, as well as the features due to bandlike behavior. With some additional refinements, these methods could be used as an alternative to reference compounds.

非共振X射线发射光谱学被应用于比较富含氮的化合物硝酸铵、三硝基甲苯和环三甲撑三硝基胺。这些化合物是结晶和分子结构在工业和军事应用中具有重要代表性的典型。通过对每种物质的谱学特征进行分析，并与系统电子结构的特征相对应，完成了该分析。该分析是通过理论模拟发射光谱以及详细考察分子轨道和态密度来实现的。我们发现，所采用的两种理论方法（冻结轨道密度泛函理论和实空间格林函数模拟）能够半定量地解释观察到的光谱，并能够预测源自不同化学复合体的特征。计算结果与数据的比较为我们揭示了特定分子轨道的电子贡献，以及由带状行为产生的特征。经过一些额外的改进，这些方法可以作为参考化合物的替代品被使用。