NX(X=F,Cl,Br)分子结构与极化函数f轨道的作用

Molecular Structure for NX(X=F,Cl,Br) and the Contribution of Polarization Functions f Orbitals

用密度泛函理论的Becke3LYP方法,计算了NX(X=F,Cl,Br)的激发态b1Σ+和基态X3Σ-,并对比不含f轨道的基集合cc-pvDZ和6-311+G与含f轨道的基集合6-311+G(3df)的计算结果,发现极化函数f轨道对NCl和NBr的键长与谐振频率ωe有明显改进作用,即f轨道对成键有贡献,而f轨道对NF的Re和ωe则无明显作用.同时,基于能量共振转移的需要,用NF代替O2-I红外激光系统的O2是不适宜的,而用NCl和NBr代替则是可能的.

Excited states b(1) Sigma(+) and ground states X-3 Sigma(-) for molecules NX (X = F, Cl, Br) have been calculated using density functional theory(DFT) Becke 3LYP. In comparison of the calculated results with f orbitals basis set 6-311 + G(3df) and that without f orbitals basis sets cc-pvDZ and 6-311 + G*, it is instructive to notice that the polarization function f orbitals significantly contribute to improve in bond lengths R-e and vibration frequencies omega(e) for NCl and NBr, but not for NF. Therefore, the f orbitals not only play some subtle aspects in bonding for lanthanides and actinides, but also for the elements lighter than lanthanum.