How do I know if the reconstruction in the picture is a 2 x 2 reconstruction or not?
I believe that this corresponds to a 2x2 reconstruction because there's an even horizontal and vertical distance between the half-order and the full-order points in the corners of the pattern but I don't really understand how this is any different from a 4x4 or so.
On the Wikipedia page on LEED the following image is shown, representing the superposition of two different patterns, the 2x1, and the 1x2 patterns. These look identical to me apart from the direction of the drawn rectangle which thus far I have presumed to be a choice of the individual.
Can these projections also indicate if such a surface is faceted? If so, how can this be deduced?