季戊四醇四硝酸酯晶体能带结构和起爆机理的DFT研究

DFT Studies on Energy Band Structure and Detonation Mechanism of Pentaerythritol Tetranitrate Crystal

对季戊四醇四硝酸酯 ( PETN)晶体进行 DFT-B3 LYP计算 ,求得其晶格能为 -1 .0 0 0 e V,与实验值相近 .前沿能带平坦 ,表明分子轨道能态受分子晶体场的影响较小 .硝基 O原子的较大贡献和酯 O原子的较小贡献共同组成价带上沿态密度 ,而空带下沿则由硝基 O和硝基 N原子共同组成 ,说明— NO2 基易于接受电子 .O—C键的重叠布居数明显比所有其它键的小 ,加之 O— C键鞍点偏离其中点 0 .0 2 2 nm,表明该键易于优先异裂起爆 .由重叠布居数可知 ,分子间 O…H存在较小的相互作用 ,[1 1 0 ]方向的撞击将使 O…H距离靠近 ,因而相互作用加强 ,还使 O—C键上的电子向 O原子转移 ,并大大减小该键的重叠布居数 ,因而促进了该键的异裂 .

The electronic structural properties of pentaerythritol tetranitrate crystal lattice have been studied at B3LYP level by DFT method. The calculated crystal lattice energy is -1.000 eV, which is comparable to experimental value. The frontier energy bands are generally quite flat, indicating that the molecular orbital is hardly perturbed by the crystalline environment. The oxygen atoms in nitro group make up lower energy bands with a small component from the ester oxygen, whereas both the nitrogen and oxygen atoms in nitro group make up the higher energy bands. The overlap population of the O—C bond is smaller or much smaller than those of another bonds. Also, the O—C bond saddle point is deviated from the midway by 0.022 nm, indicating that the O—C bond is polarized and is prone to heterolysis resulting in detonation. The [110] shocks result in a closer O…H contacting, which promotes the interaction between the nitro oxygen of one molecule and the hydrogen atom of another molecule, makes electron transfer to ester oxygen of the O—C bond, greatly reduces the overlap population on the O—C bond and thus facilitates the heterolysis rupture of this bond.