三硝基均苯三酚及其碱金属盐晶体的周期性密度泛函理论研究

对三硝基均苯三酚(TNPG)及其碱金属盐晶体进行DFT-B3LYP周期性计算研究, 求得其能带和电子结构, 探讨了结构-性能关系. 研究结果表明, 晶胞结构参数的计算值与实验值吻合较好. TNPG的导电性介于半导体和绝缘体之间, 而其碱金属盐均为半导体. 金属离子的引入使TNPG阴离子和金属阳离子通过配位键形成三维无限网状结构, 这种网状结构与晶体的半导体性质相关联. TNPG及其碱金属盐的前线轨道主要是由C—NO₂的原子轨道组成, 配位水和金属离子对前线轨道的组成没有贡献. TNPG碱金属盐的带隙均比TNPG的小, 根据“最易跃迁原理”可推测碱金属盐均比TNPG敏感, 这与实验事实相符. 同时, 金属离子的引入增大了酚羟基上的氧原子的活性, 这也可能是导致碱金属盐比TNPG敏感的原因之一.

Periodic Density Functional Theory Studies on Trinitrophloroglucinol and Its Alkali Metal Salts

The banding and electronic structures of trinitrophloroglucinol (TNPG) and its alkali metal salts have been investigated at B3LYP level by a periodic density functional theory (DFT) method. The relationship between structure and property was discussed. The calculated lattice parameters are in good agreement with the experimental values. The results show that the conductivity of TNPG is between the semiconductor and insulator, however, its alkali metal salts are electrical semiconductors. The existence of metallic atoms results in the packing of anions and cations through coordinated bonds to form a network structure. And this is correlated with the semiconducting property of the alkali metal salts. The frontier orbitals of TNPG and its alkali metal salts all mainly consist of atomic orbitals of C—NO₂ groups, but the coordinated water molecules and metallic ions do not have any contributions to it. The values of band gaps of all the alkali metal salts are smaller than that of TNPG. Consequently, the alkali metal salts are more sensitive than TNPG, according to the “principle of the easiest transition”, and this prediction is in good agreement with the experimental result. In addition, the existence of metallic atoms makes the phenol oxygen atoms more reactive which may be one of the reasons that alkali metal salts are more sensitive than TNPG.