HMX分子异构体性质的理论研究

在含时密度泛函理论的框架下,首先选取了三个软件包（PWSCF软件包、CPMD软件包、OCTOPUS软件包）和两种泛函（PBE泛函、LDA泛函）构成的五种方案优化了HMX单分子异构体的四种构型（Boat构型与Boat-Boat构型属于C2群,Chair构型属于Ci群,Boat-Chair构型属于C1群）,并计算了各构型的相对总能量关系,所得结论与前人有所不同,Boat-Boat构型总能量不是最低;其次计算了HMX单分子异构体的态密度,结果表明除Boat-Chair型外其他构型均具有明显的能级分裂特征,各构型均具有绝缘体特征且Boat型能隙最大;最后计算了各构型的光吸收截面,发现Boat构型的HMX分子的光吸收截面中能观察到的显著的峰最多,其次是Boat-Boat构型、Boat-Chair构型,Chair构型最少.

Theoretical study on properties of HMX isomers

Within the framework of Time-Dependent Density Functional Theory, we chose five methods （three software packages： PWSCF, CPMD and OCTOPUS; two fuctionals： PBE and LDA） to optimize the geometries of HMX and calculate each isomer＇s relative total energy relationship. We obtain four stable isomers. Isomers of Boat and Boat-Boat belong to C2 symmetry group. Chair isomer belongs to Ci symmetry group. Boat-Chair isomer belongs to C1 symmetry group. However, the results of relative total energy relationship are disagreement with the previous research, which is that the total energy of Boat-Boat isomer is not the lowest. The results which we calculate the density of states of the isomers of HMX show every isomer has the level splitting except the type of Boat-Chair. We also found evident insulator characters in four isomers of HMX and the type of Boat has the biggest energy gap. Finally, we calculate the optical absorption spectra of four isomers of HMX. The most wave peaks have been found in the optical absorption spectra of isomer of Boat, then isomers of Boat-Boat and Boat-Chair, and the least in Chair isomer.