卤素氟化物ClFO3的结构与性能的理论研究

卤素氟化物是一类反应活性很强的物质，在诸多领域有重要应用。本文采用量子化学密度泛函理论（DFT）B3LYP/6-31G(2df)方法，对卤素氟化物ClFO3的七种异构体进行了几何优化和振动频率分析，结果表明它们均对应于势能面上的稳定构型。这七种异构体中，Cl原子作为中心原子，与1个F原子和3个O原子直接成键形成的分子结构能量最低，为最稳定结构。根据统计热力学原理，计算了标题物的标准热力学函数，包括摩尔热容（Cop,m）、摩尔熵（Som）和摩尔焓（Hom）。理论计算所得结构参数和与热力学函数均与文献报道的实验值相符，说明了所用理论方法的可靠性。借助于原子化反应和生成反应计算了其生成焓及其与甲烷和水反应的热效应。在DFT优化分子结构的基础上，采用力场方法得到ClFO3的最可能堆积方式属于Pbca空间群，进一步采用DFT GGA-RPBE方法优化其晶体结构，并计算能带结构和态密度，发现其带隙较宽（4.61eV），表明其具有较好的稳定性。在Fermi能级附近，ClFO3晶体中的导带主要来自于O和F原子的2p轨道的贡献，而价带主要来自于Cl原子的2p轨道的贡献。

Theoretical Study on the Structure and Properties of ClFO3

Halogen fluorides are usually corrosive and reactive, and used widely in industry. In this paper, seven isomers of halogen fluoride ClFO3 were studied and their geometries were optimized using the density functional theory (DFT) B3LYP/6-31G(2df) method. Normal mode analysis for each isomer resulted in no imaginary frequencies, indicating that all structures correspond to the local minima on the potential energy surface. Among the isomers, the most stable one has the form that the central chlorine atom bonded with one fluorine and three oxygen atoms. On the basis of the principle of statistical thermodynamics, the standard molar heat capacity, entropy, and enthalpy from 200 to 800 K were evaluated. The calculated results of geometrical parameters and thermodynamic functions agree with the experimental values. The atomization reaction and formation reaction were used to calculate the heat of formation of the title compound. The force field method was used to predict the possible crystal structure based on the molecular structure and the resulted crystal structure had the Pbca space group and was further refined by DFT. The band gap of the crystal is large (4.61 eV), which indicates that ClFO3 is relatively stable. The lower unoccupied crystal orbitals are mainly from the 2p states of F and O atoms and the higher occupied crystal orbitals are mainly the contributions of 2p states of Cl atom.