The DFT(B3LYP) method with Aug-cc-pvtz basis set is used to investigate the equilibrium structures, atomic charge distributions, dipole moments, harmonic frequencies and total energies of CO molecule under different external electric fields. The results show that the bond length is in excellent agreement with the experimental results. The bond lengths are proved to be increasing and harmonic frequencies are proved to be decreasing, the total energy is found be first decreasing, and then increasing, with the variation of external field, and the dipole moments are detected to be increasing (Numerical results) with the variation of reverse external field. The potential energy curves of CO molecule under different external fields are also obtained by DFT(B3LYP) method with Aug-cc-pvtz basis set. The potential energy function without external electric field is fitted by Morse potential. It is found that the fitting parameters are good agreement with experimental values. The potential energy curves without external electric field is smaller than with external electric field.
