Abstract: Excited states b1Σ＋ and ground states X3Σ－ 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 Re and vibration frequencies ωe 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.

Key words: NX(X=F,Cl,Br) molecules, Density functional theory, Polarization function f orbitals