For tarnsition metals, talking about polarization is a bit difficult. Although it is gnerally true that for the even elecrons, we can usually choose spin-unpolarized calculation; however, in some cases electrons tend to be unpaired. Suppose, we work on Pd bulk and surfaces. Its electronic configuration is 4s2 3d8. According to chemists, the d-electrons are unpaired and so we should use spin-polarization calculation. However, in ome papers, I see that they take a spin-unpolarized calculation. Its atomic number is 46. In these cases users may be confused. Any detail discussion about this issue will be appreciated.