Molecular structure for NX(X = F, Cl, Br) and the contribution of polarization functions f orbitals

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.