{#sec:results}
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Once converged charge densities were obtained, bandstructures were calculated along the $M$–$\Gamma$–$X$ high-symmetry pathway (as shown in Fig. \[fig:tetBZ\] in Appendix \[sec:bravais\]), using at least 20 *k*-points between high-symmetry points. For comparative purposes, the bandstructures have all been aligned at the valence band maximum (VBM).

![Full band structure of the 40-layer tetragonal system, calculated using PW (<span style="font-variant:small-caps;">vasp</span>). Bulk and 1/4 ML doped structures are shown.[]{data-label="fig:bandscomparison"}](d1vasp "fig:"){width="\linewidth"} \[fig:d1vasp\]

Figure \[fig:bandscomparison\] contrasts bulk and doped bandstructures for the 40-layer PW calculation. DZP and SZP results are similar on this scale and are omitted in the interest of clarity in the diagram. As discussed in App. \[sec:zfold\], it is evident from the bulk values that the elongated cells have led to the folding of two CBM valleys towards the $\Gamma$-point. Also visible is the difference the doping potential makes to the system; what was the lowest unoccupied orbital in the bulk is now dragged down in energy by the extra ionic potential. It is of note that the region near $\Gamma$, corresponding to the $k_{z}$ valleys which can be modeled as having different effective masses to the $k_{x,y}$ valleys,[@Qian05] is brought lower than the region corresponding to the $k_{x,y}$ valleys 