Quantum chemical study of reaction mechanism between plutonium and nitrogen.

The study of the reaction between plutonium and nitrogen is helpful in further understanding the interaction between plutonium and air molecules. Currently, there is no research on the microscopic reaction mechanism of plutonium nitridation reactions. Therefore, the microscopic mechanism of the Pu with N2 gas phase reaction is explored in this study, based on density functional theory (DFT) using different basis functions. In this paper, the geometry of stationary points on the potential energy surface is optimized. In addition, the transition states are verified by frequency analysis and intrinsic reaction coordination (IRC). Finally, we obtained the reaction potential energy curve and micro reaction pathways. Analysis of the reaction mechanism shows that the reaction of Pu with N2 has two pathways. Pathway 1 (Pu + N2 → R1 → TS1 → PuN2) has a T-shaped transition state and pathway 2 (Pu + N2 → R2 → TS2 → PuN + N) has an L-shaped transition state. Both transition states have only one imaginary frequency. According to the comparison of the energy at each stagnation point along the two pathways, and the heat energy emitted by the two reaction paths, we found that pathway 1 is the main reaction pathway. The nature of Pu-N bonding evolution along the pathways was studied by atoms in molecules (AIM) and electron localization function (ELF) topological approaches. In order to analyze the role of the plutonium atom 5f orbital in the reaction, the variation in density state along the pathways was measured. Results show that the 5f orbital mainly contributes to the formation of Pu-N bonds, and the influence of temperature on the reaction rate is revealed by calculating the rate constants of the two reaction pathways.

Molecular dynamics research on effect of doping defects on properties of PETN.

To investigate the effect of doping defects on properties of pentaerythritol tetranitrate (PETN), the "perfect" and doping defective crystal models of PETN containing pentaerythritol (PE), pentaerythritol mononitrate (PEMonoN), pentaerythritol dinitrate (PEDiN), and pentaerythritol trinitrate (PETRIN) were established, respectively. Molecular dynamics (MD) method was applied to perform simulations, and sensitivity, detonation performance, and mechanical properties were calculated and compared. The results indicate that compared with PETN (1 1 0) supercell model, the interaction energy of trigger bond and cohesive energy density of the doped defect models decreased by 2.21~12.43 kJ mol-1 and 0.0219~0.0421 kJ cm-3, respectively, indicating that the sensitivity of defective models increases and the safety decreases. The density, detonation velocity, and detonation pressure of the doped defect model decreased by 0.018~0.061 g cm-3, 77.833~272.809 m s-1, and 0.746~2.544 GPa, respectively, and the oxygen balance is declined, indicating that the energy density of PETN decreased and the power decreased. Doped defects also cause the elastic modulus, bulk modulus, and shear modulus of PETN to decrease by 0.75~2.16 GPa, 0.44~0.89 GPa, and 0.30~0.89 GPa, respectively. The ratio of bulk modulus to shear modulus and Cauchy pressure increased by 0.05~0.28 GPa and 0.09~1.13 GPa, respectively, indicating that the deformation resistance, fracture strength, and hardness of the doped defect model decrease, stiffness decreases, and flexibility and ductility increase.