1          0.6107               0.6102
                            DZP                               40         1          0.6218     
   (<span style="font-variant:small-caps;">siesta</span>)     60         1          0.6194     
                                                              80         1          0.6154     
                                                             120         1          0.6145     
                                                             160         1          0.6151               0.6145
                            SZP                               40         1          0.8392     
   (<span style="font-variant:small-caps;">siesta</span>)     60         1          0.8349     
                                                              80         1          0.8315     
                                                             120         1          0.8311     
                                                             160         1          0.8315     
                                                             200         1          0.8310               0.8309
  -------------------------------------------------------- -------- ------------ ------------- --------------------------

  : Energy levels of tetragonal bulk Si structures. (For details of calculation parameters, see Sec. \[sec:methods\])[]{data-label="tab:bulkSi"}

Increasing the $z$-dimension of the cell leads to successive folding points being introduced as the Brillouin zone (BZ) shrinks along $k_{z}$ (see App. \[sec:bravais\]). This has the effect of shifting the conduction band minima in the $\pm k_{z}$ directions closer and closer to the $\Gamma$ point (see Fig. \[fig:folding\]) and making the bandstructure extremely dense when plotting along $k_{z}$. This results in the value of the lowest unoccupied eigenstate at $\Gamma$ being lowered as what were originally other sections of the band are successively mapped onto $\Gamma$, and after a sufficient number of folds the value at $\Gamma$ is indistinct from the original conduction band minimum (CBM) value. The effects of this can be seen in Table \[tab:bulkSi\], which describes increasingly elongated tetragonal cells of bulk Si. When we then plot the bandstructure in a 