用杂化CIS-DFT方法研究外电场对乙烯激发态的影响

采用杂化CIS-DFT方法研究了外电场对乙烯分子基态和激发态性质的影响,结果表明外电场对分子几何结构,总能量,偶极矩,极化率,振子强度和激发能有显著影响.CIS-DFT的优点在于能确定外场下分子的对称性,给出正确的激发顺序以及分子轨道的电子组态,由此导出乙烯分子的激发态,结果与实验一致.首次研究了乙烯分子的外电场效应.与其他从头算方法相比,杂化CIS-DFT方法计算精确和效率相对较高,可用于研究大分子体系.

External electric field effects on the electronic excited states of ethylene

The present work devotes to study the effects of external electric field on the molecular properties of ethylene employing a hybrid method which combines the single-excitation configuration interaction(CIS) with density function theory(DFT),i.e.,CIS-DFT(B3LYP).It is found that the effects of electric field on the molecular geometry(D_(2h), D_(2d) and C_(2v)),dipole moment,transition dipole moment,polarizability,and particularly,excitation energy of ethylene are rather remarkable.The advantages of hybrid CIS-DFT method are that it can determine the symmetry of molecule and give out the correct order of excitation as well as the MO electronic configuration,from which the electronic excitation states of ethylene have been easily derived out,and most of them are in agreement with the experiment.The consideration of the effects of external electric field on ethylene molecule may be the first time.Compared with other ab initio methods,the method present here is relatively accurate and low in computation cost.We expect that it can be used to other closed-shell molecules.