Spin polarization effect for Co₂ molecule

The density functional theory (DFT)(b3p86) of Gaussian 03 has been used to optimize the structure of the Co_2 molecule, a transition metal element molecule. The result shows that the ground state for the Co_2 molecule is a 7-multiple state, indicating a spin polarization effect in the Co_2 molecule. Meanwhile, we have not found any spin pollution because the wavefunction of the ground state is not mingled with wavefunctions of higher-energy states. So for the ground state of Co_2 molecule to be a 7-multiple state is the indicative of spin polarization effect of the Co_2 molecule, that is, there exist 6 parallel spin electrons in a Co_2 molecule. The number of non-conjugated electrons is the greatest. These electrons occupy different spacial orbitals so that the energy of the Co_2 molecule is minimized. It can be concluded that the effect of parallel spin in the Co_2 molecule is larger than the effect of the conjugated molecule, which is obviously related to the effect of electron d delocalization. In addition, the Murrell- Sorbie potential functions with the parameters for the ground state and the other states of the Co_2 molecule are derived. The dissociation energy De for the ground state of Co_2 molecule is 4.0489eV, equilibrium bond length R_\rm e is 0.2061 nm, and vibration frequency \omega _\rm e is 378.13 cm^ - 1. Its diatomic molecule force constants f_2, f_3, and f_4 are 2.4824 aJ\cdotnm^ - 2, -7.3451 aJ\cdotnm^ - 3, nd 11.2222 aJ\cdotnm^ - 4 respectively(1 aJ=10^-18 J). The other spectroscopic data for the ground state of Co_2 molecule \omega_\rm e\chi _\rm e, B_\rm e, and \alpha_\rm e are 0.7202 cm^-1, 0.1347 cm^-1 , and 2.9120\times 10^-1 cm^-1 respectively. And \omega_\rm e\chi _\rm e is the non-syntonic part of frequency, B_\rm e is the rotational constant, \alpha_\rm e is revised constant of rotational constant for non-rigid part of Co_2 molecule.