Ciezak Jennifer A, Trevino S F
U.S. Army Research Laboratory, Weapons and Materials Research Directorate, Aberdeen Proving Ground, Maryland 21005, USA.
J Phys Chem A. 2006 Apr 20;110(15):5149-55. doi: 10.1021/jp057098u.
Solid-state geometry optimizations and corresponding normal-mode analysis of the widely used energetic material cyclotrimethylenetrinitramine (RDX) were performed using density functional theory with both the generalized gradient approximation (BLYP and BP functionals) and the local density approximation (PWC and VWN functionals). The structural results were found to be in good agreement with experimental neutron diffraction data and previously reported calculations based on the isolated-molecule approximation. The vibrational inelastic neutron scattering (INS) spectrum of polycrystalline RDX was measured and compared with simulated INS constructed from the solid-state calculations. The vibrational frequencies calculated from the solid-state methods had average deviations of 10 cm(-1) or less, whereas previously published frequencies based on an isolated-molecule approximation had deviations of 65 cm(-1) or less, illustrating the importance of including crystalline forces. On the basis of the calculations and analysis, it was possible to assign the normal modes and symmetries, which agree well with previous assignments. Four possible "doorway modes" were found in the energy range defined by the lattice modes, which were all found to contain fundamental contributions from rotation of the nitro groups.
使用密度泛函理论，采用广义梯度近似（BLYP和BP泛函）以及局域密度近似（PWC和VWN泛函），对广泛使用的含能材料环三亚甲基三硝胺（RDX）进行了固态几何优化及相应的简正模式分析。发现结构结果与实验中子衍射数据以及先前基于孤立分子近似报道的计算结果吻合良好。测量了多晶RDX的振动非弹性中子散射（INS）光谱，并与基于固态计算构建的模拟INS进行了比较。从固态方法计算得到的振动频率平均偏差为10 cm⁻¹或更小，而先前基于孤立分子近似发表的频率偏差为65 cm⁻¹或更小，这说明了考虑晶体作用力的重要性。基于计算和分析，能够确定简正模式和对称性，这与先前的归属吻合良好。在由晶格模式定义的能量范围内发现了四种可能的“门道模式”，均发现其包含硝基旋转的基本贡献。
