为了寻找兼具优异爆轰性能和良好热力学及动力学稳定性的高能材料,本文设计了15个硝基尿酸化合物,运用密度泛函理论,对其性质进行了研究.通过半经验的K-J方程和比冲量预测了其爆炸性能,结果表明,所设计分子的爆热、分子密度、爆炸速率和爆炸压强同硝基取代基数目之间存在较强的线性关系.三硝基尿酸和四硝基尿酸衍生物的爆炸速率超过了8.0 km/s,爆炸压强超过了30 GPa,并且大多数衍生物的比冲量要高于目前经常使用的炸药黑索金.通过计算N—NO2键的解离能、特征落高、分子的自由空间预判了衍生物的稳定性和撞击感度,结果显示,绝大多数分子有大于80 k J/mol的键解离能.本文的理论结果可以为实验上设计合成新的高能材料提供一些有用的信息.
A dynamic method is employed to study the reaction mechanisms of CH3CH2OCF3 with the hydrogen trioxy （HOOO） radical. In our paper, the geometries and harmonic vibrational frequencies of all the stationary points and minimum energy paths （MEPs） are calculated at the MPW1K/6-31＋G（d,p） level of theory, and the energetic information along MEPs is further refined by the CCSD/6-31＋G（df, p） level of theory. The rate constants are evaluated with the conventional transition-state theory （TST）, the canonical variational transition-state theory （CVT）, the microcanonical variational transition-state theory （μVT）, the CVT coupled with the small-curvature tunneling （SCT） correction （CVT/SCT）, and the μVT coupled with the Eckart tunneling correction μVT/Eckart） based on the ab initio calculations in the temperature range of 200-3000 K. The theoretical results are important in determining the atmospheric lifetime and the feasible pathways for the loss of HFEs.
A theoretical investigation of the reaction mechanisms for C-H and C-C bond activation processes in the reaction of Ni with cycloalkanes C,,H2. （n = 3-7） is carried out. For the Ni ＋ CnH2, （n = 3, 4） reactions, the major and minor reaction channels involve C-C and C-H bond activations, respectively, whereas Ni atom prefers the attacking of C-H bond over the C-C bond in CnH2n （n = 5=7）. The results are in good agreement with the experimental study. In all cases, intermediates and transition states along the reaction paths of interest are characterized, It is found that both the C-H and C-C bond activation processes are proposed to proceed in a one-step manner via one transition state. The overall C-H and C-C bond activation processes are exothermic and involve low energy barriers, thus transition metal atom Ni is a good mediator for the activity of cycloalkanes CnH2n （n = 3 -7）.
