dimensions of the unit cell. To calculate the energies and forces for each lateral position a $10\times10$ grid is constructed in the x-y plane, resulting in a spacing of $\unit[\sim0.25]{\AA}$ between the grid points. A cubic spline interpolation is applied to refine this grid by a factor of 10 and create smooth energy- and force-surfaces. To simulate the usual experimental setup, we perform our scans keeping the load at a constant value which implies that the distance of the slabs needs to adapt. To this end the distance between the slabs is varied in 6 steps for each of the 100 grid-points, recording the respective volume $V$ and the total energy of the relaxed cell $E^{\mathrm{R}}$ which are fitted to a second order polynomial. The uniaxial pressure on the cell can now be evaluated by calculating the first derivative of $E^{\mathrm{R}}$ with respect to $V$ at each lateral position, namely $p=-\partial E^{\mathrm{R}}\,/\,\partial V$. The corresponding loading force $L$ is then obtained by multiplying the pressure with the cross-section area $A$ of the unit cell, $L=p\,A$. Choosing a load (given derivative of the energy vs. volume functions) we recalculate the respective energies and forces at each of the 100 grid points 