外电场下4-氟苯酚分子的分子结构和解离特性

4-氟苯酚是一种用途广泛的芳香族化合物，同时也是具有毒性的有机污染物之一，对环境和人体都有巨大危害.研究其在外电场作用下的降解机理具有重要意义.本文采用密度泛函方法(DFT)方法和含时密度泛方法(TD-DFT)在B3LYP/6-311G+(2d, 2p)基组水平上，研究了4-氟苯酚分子在不同外加电场(0-0.03 a.u.)下的几何结构、光谱特性、解离特性.结果表明，外加电场对4-氟苯酚分子的结构和性质有较大影响，随着X(C-F键)方向外电场的增加，4-氟苯酚分子C-F键的键长增大、分子体系总能量逐渐减小、偶极矩逐渐增大、能隙逐渐减小. 4-氟苯酚分子红外光谱的最强峰发生红移，紫外吸收光谱吸收峰峰值先增大后减小，峰型变宽，4-氟苯酚分子解离势能逐渐减小，说明4-氟苯酚分子在外电场作用下趋于解离.该研究对4-氟苯酚污染物分子的外电场降解提供参考.

Molecular structure and dissociation characteristics of 4-Fluorophenol under external electric field

4-Fluorophenol is a widely used aromatic compound and one of toxic organic pollutants, which has great harm to the environment and human body. It is of great significance to study its degradation mechanism under external electric field. In this paper, the density functional method (DFT) and the time-dependent density universal method (TD-DFT) are used to study the geometric structure, spectral characteristics and dissociation characteristics of 4-fluorophenol molecules under different applied electric fields (0-0.03a.u.) at the B3LYP/6-311G+2D2P basis set level. The results show that the applied electric field has a great influence on the structure of 4-fluorophenol molecules. With the increase of the external electric field in the direction of X (C-F bond), the bond length of C-F bond of 4-fluorophenol molecules increases, the total energy of molecular system gradually decreases, the dipole moment gradually increases and the energy gap gradually decreases. The strongest peak of the infrared spectrum of 4-fluorophenol molecule is red-shifted, the peak value of the absorption peak of ultraviolet absorption spectrum first increases and then decreases, and the dissociation potential energy of 4-fluorophenol molecule gradually decreases, which indicates that 4-fluorophenol molecule tends to dissociate under the action of external electric field. This study provides a reference for the degradation of 4-fluorophenol pollutant molecules by external electric field.