环形C18在外电场下的基态性质和激发特性  

Study on the ground state properties and excitation properties of C18 under different external electric fields

作　　者：李世雄 陈德良 张正平 隆正文 秦水介[4] Li Shi-Xiong;Chen De-Liang;Zhang Zheng-Ping;Long Zheng-Wen;Qin Shui-Jie(School of Physics and Electronic Science,Guizhou Education University,Guiyang 550018,China;College of Big Data and Information Engineering,Guizhou University,Guiyang 550025,China;College of physics,Guizhou University,Guiyang 550025,China;Key Laboratory of Photoelectron Technology and Application,Guizhou University,Guiyang 550025,China)

机构地区：[1]贵州师范学院物理与电子科学学院,贵阳550018 [2]贵州大学大数据与信息工程学院,贵阳550025 [3]贵州大学物理学院,贵阳550025 [4]贵州大学,贵州省光电子技术及其应用重点实验室,贵阳550025

出　　处：《物理学报》2020年第10期98-109,共12页Acta Physica Sinica

基　　金：国家自然科学基金青年科学基金(批准号:11804065);中央引导地方科技发展专项资金(批准号:黔科中引地[2019]4012号)资助的课题.

摘　　要：采用密度泛函理论方法(ωB97XD/def2-TZVP)研究了沿不同方向(x,y,z)加电场对环形C18的基态几何结构、能量、电子结构、芳香性、红外及拉曼光谱特性的影响;继而采用含时的TD-ωB97XD方法研究了C18在外电场下的激发特性.研究结果表明:外电场导致分子对称性降低,偶极矩随外电场的增加逐渐增加,体系总能量和LUMO-HOMO能隙随着外电场的增加一直减小.外电场将改变环上π电子的离域特征以及分子芳香性,如分子z方向加入电场将减弱π电子离域性及分子芳香性,分子x或y方向加入电场可以增强π电子离域性及分子芳香性.外电场将改变红外光谱特征,如谐振频率的移动以及红外峰的增强或减弱.外电场对环形C18的激发特性影响较大,如当分子y方向加电场时,激发波长发生红移;同时对振子强度有很大影响,原来振子强度很强的激发态变弱或成为禁阻跃迁,而原来振子强度很弱或禁阻的激发态变强.可以通过改变外电场来控制C18的基态性质和光谱特性,促进C18在分子器件等纳米领域的应用.In this work,density functional theory method with the ωB97 XD/def2-TZVP level is carried out to investigate the ground state structures,energy,electronic structures,aromaticity,infrared and Raman spectra of cyclo[18]carbon under different external electric field in the x,y and z direction of cyclo[18]carbon molecule.The excitation properties(the first 48 excited states containing excited energies,excited wavelengths and oscillator strengths) of cyclo [18] carbon are calculated by the time-dependent density functional theory method(TD-ωB97 XD) with the def2-TZVP basis set under the same external electric field.The results show that cyclo[18]carbon can be elongated in the x or y direction under the electric field,and some C-C bond lengths can be elongated or shortened under the electric field.Meanwhile,the calculated results show that electric dipole moment is proved to be increasing with the increase of the external field intensity,but the total energy and LUMO-HOMO gap are proved to decrease with the increase of external field intensity.Moreover,addition of electric field can modify the electron delocalization and molecular aromaticity,such as external electric field in z direction can lower the electron delocalization and molecular aromaticity and external electric field in x or y direction can enhance the electron delocalization and molecular aromaticity.The addition of electric field can modify the infrared spectra,such as shift of vibrational frequencies and strengthening of infrared peaks.Furthermore,the calculated results indicate that the external electric field has significant effects on the excitation properties of cyclo [18] carbon.The increase of the electric field intensity can lead to the redshift of transition wavelengths(such as the first excited state).With the change of the electric field intensity,the stronger excited state(with the bigger oscillator strength) can become weak(with the small oscillator strength)or optically inactive(with the oscillator strength of zero).Meanwhile,the weak or o

关 键 词：C18 外电场 基态 激发特性 

分 类 号：O561[理学—原子与分子物理]