Rectangular band model electronic energy

The qualitative behavior predicted from the rectangular d band model can actually be seen in self-consistent DFT calculations, where the shape of the DOS is explicitly calculated. For example, we show this in the lower part of Figure 2.22 where the bulk and surface PDOS projected on to the valence d orbitals is plotted for bulk Zr and Ru and for Zr and Ru (0001) surfaces. For both Zr and Ru, the d PDOS associated with the surface atoms is narrower than that of the bulk. For Zr with <5 d electrons, the surface d PDOS moves down in energy ( 0.1 eV) relative to the... 

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