钼、钨四重键化合物电子光谱的含时密度泛函理论研究  

Time-dependent Density Functional Theory Studies on the Electronic Spectra of Mo_2 and W_2 Quadruply Bonded Compounds

作　　者：仇毅翔[1] 王曙光[1] 

机构地区：[1]上海交通大学化学化工学院,上海200240

出　　处：《高等学校化学学报》2011年第1期161-169,共9页Chemical Journal of Chinese Universities

基　　金：国家自然科学基金(批准号:20773086)资助

摘　　要：运用含时密度泛函理论(TD-DFT),对具有代表性的钼、钨四重键化合物M2Cl84-,M2Cl4(PMe3)4,M2(O2CCH3)4和M2(PhNCHNPh)4(M=Mo,W)的低占据电子激发能进行了计算,系统地考察了局域(LDA)、离域(GGA)和杂化(Hybrid)泛函对金属四重键化合物中d-d跃迁和电荷转移跃迁(CT)计算的适用性.研究结果表明,LDA和GGA泛函对d-d跃迁激发能计算的较为准确,但对CT跃迁激发能的计算误差较大.出现这种情况的原因在于CT跃迁具有显著的离域特征,采用不含时泛函(LDA或GGA)代替含时泛函后未能对电子在CT跃迁中的长程行为给予正确的描述.包含HF交换项的杂化泛函可以对CT跃迁激发能给予一定的修正,但却降低了d-d跃迁激发能的计算准确性.如果对两种跃迁同时进行严格而准确的描述,则需将准确的含时泛函应用于含时密度泛函理论的计算中.The low-lying electronic excited states of M2Cl4-8,M2Cl4（PMe3）4,M2（O2CCH3）4 and M2（PhNCHNPh）4（M=Mo,W） were studied with the time-dependent density functional theory（TD-DFT）.Furthermore,the applicability of a series of functionals,such as LDA,GGA and hybrid functional,for calculating d-d and charge-transfer（CT） transitions of quadruply bonded compounds had been tested.It is found that the LDA and GGA functionals provide accurate description of the d-d transitions,but yields substantial errors for the excitation energies of CT transitions.The electrostatic attraction between the separated charges in long-range excited charge-transfer states originates from the non-local Hartree-Fock（HF） exchange potential and is a non-local property.Present-day TD-DFT method employing pure exchange-correlation functionals（LDA or GGA） does not capture this effect and therefore fails to describe CT excited states correctly.The hybrid functionals include parts of HF exchange provide accurate results for the CT transition energy,but the errors in the d-d transition energies were much larger than those predicted by the LDA and GGA functionals.In order to simultaneously obtain the accurate descriptions of both d-d and CT transitions of quadruply bonded compounds,we will look forward to the strict time-dependent non-local functional is applied to the calculation of TD-DFT method.

关 键 词：金属四重键化合物 含时密度泛函理论 电子光谱 D-D跃迁 电荷转移跃迁 

分 类 号：O641[理学—物理化学]