Axes scale

[YitengDang]

The scale of the axes seems hard to fix in the simulation app. For correct positioning of the cells, the ratio between x and y axes should be sqrt(3)/2. I've now used the command
set(ax, 'PlotBoxAspectRatioMode', 'manual');
set(ax, 'PlotBoxAspectRatio', [1+2*d sqrt(3)/2+2*d 1]);
when initializing the lattice. However, this does not always seem to work and resizing the window sometimes have bad effects.

[YitengDang]

Instead of imposing a rigid scaling between x and y, we let the aspect ratio be unspecified to allow for better scaling with window size changes. Note that the distances in the horizontal and vertical directions do not have the same scale in this way, but this is likely fine.