硼球烯B40在外电场下的基态性质和光谱特性

摘要

以6-31G*为基组,采用密度泛函PBE0方法研究了不同外电场(0-0.060 a.u.)对硼球烯B40的基态几何结构、电荷分布、能量、电偶极矩、能隙、红外及拉曼光谱特性的影响;继而采用含时的TD-PBE0方法研究了硼球烯B40在外电场下的电子光谱.研究结果表明:外电场的加入导致分子对称性降低,当电场从0 a.u.变化到0.060 a.u.时,偶极矩逐渐增加,体系总能量和能隙一直减小;外电场的加入将改变红外和拉曼光谱特征,如谐振频率的移动以及红外和拉曼峰的增强或减弱;外电场对硼球烯B40的电子光谱影响较大,当电场从0 a.u.变化到0.060 a.u.时,电子光谱发生红移,同时对振子强度有很大影响,原来振子强度最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得最强.可以通过改变外电场来改变B40的基态性质,以及控制B40的光谱特性.%The recent discovery of borospherene B40 marks the onset of a new class of all-boron fullerenes.External electric field can influence the structure and property of molecule.It is necessary to understand the electrostatic field effect in the borospherene B40.In this work,density functional theory method at the PBE0 level with the 6-31G* basis set is used to investigate the ground state structures,mulliken atomic charges,the highest occupied molecular orbital (HOMO) energy levels,the lowest unoccupied molecular orbital (LUMO) energy levels,energy gaps,electric dipole moments,infrared spectra and Raman spectra of borospherene B4o under the external electric field within the range of values F =0-0.06 a.u..The electronic spectra (the first 18 excited states contain excited energies,excited wavelengths and oscillator strengths) of borospherene B40 are calculated by the time-dependent density functional theory method (TD-PBE0) with the 6-31G* basis set under the same external electric field.The results show that borospherene B40 can be elongated in the direction of electric field and B4o molecule is polarized under the external electric field.Meanwhile,the addition of external electric field results in lower symmetry (C2v),however,electronic state of borospherene B40 is not changed under the external electric field.Moreover,the calculated results show that the electric dipole moment is proved to be increasing with the increase of the external field intensity,but the total energy and energy gap are proved to decrease with the increase of external field intensity.The addition of external electric field can modify the infrared and Raman spectra,such as the shift of vibrational frequency and the strengthening of infrared and Raman peaks.Furthermore,the calculated results indicate that the external electric field has a significant effect on the electronic spectrum of borospherene B40.The increase of the electric field intensity can lead to the redshift of electronic spectrum.With the change of the electric field intensity,the strongest excited state (with the biggest oscillator strength) can become very weak (with the small oscillator strength) or optically inactive (with the oscillator strength of zero).Meanwhile,the weak excited state can become the strongest excited state by the external field.The ground state properties and spectral properties of borospherene B40 can be modified by the external electric field.Our findings can provide theoretical guidance for the application of borospherene B40 in the future.