Spin polarization effect of Ni2 molecule
Chin. Phys. B, 2008, 17 (12):
The density functional theory (DFT) method (b3p86) of Gaussian 03 is used to optimize the structure of the Ni2 molecule. The result shows that the ground state for the Ni2 molecule is a 5-multiple state, symbolising a spin polarization effect existing in the Ni2 molecule, a transition metal molecule, but no spin pollution is found because the wave function of the ground state does not mingle with wave functions of higher-energy states. So the ground state for Ni2 molecule, which is a 5-multiple state, is indicative of spin polarization effect of the Ni2 molecule, that is, there exist 4 parallel spin electrons in Ni2 molecule. The number of non-conjugated electrons is greatest. These electrons occupy different spatial orbitals so that the energy of the Ni2 molecule is minimized. It can be concluded that the effect of parallel spin in the Ni2 molecule is larger than that 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 of the ground state and other states of the Ni2 molecule are derived. The dissociation energy De for the ground state of the Ni2 molecule is 1.835eV, equilibrium bond length Re is 0.2243 nm, vibration frequency $\omega$e is 262.35 cm-1. Its force constants f2, f3 and f4 are 1.1901aJ.nm2, --5.8723aJ.nm-3, and 21.2505 aJ.nm-4 respectively. The other spectroscopic data for the ground state of the Ni2 molecule $\omega$e$\chi$e, Be and $\alpha$e are 1.6315cm-1, 0.1141 cm-1, and 8.0145x10-4cm-1 respectively.