  We present a state-of-the-art density functional theory (DFT) study which
models crucial features of the partially disordered orbital order stacking in
the prototypical layered transition metal dichalcogenide 1T-TaS2 . Our results
not only show that DFT models with realistic assumptions about the orbital
order perpendicular to the layers yield band structures which agree remarkably
well with experiments. They also demonstrate that DFT correctly predicts the
formation of an excitation pseudo-gap which is commonly attributed to
Mott-Hubbard type electron-electron correlations. These results highlight the
importance of interlayer interactions in layered transition metal
dichalcogenides and serve as an intriguing example of how disorder within an
electronic crystal can give rise to pseudo-gap features.
