Convergent-beam RHEED patterns from the (100) face of MgO at 100 keV w
ere calculated using the multislice method with an incident cylindrica
l wave. Calculated patterns were compared with energy filtered pattern
s collected in a modified Philips 420 TEM from air cleaved MgO. The qu
alitative agreement between theoretical and experimental patterns was
very good, but the quantitative agreement was only fair. The lack of q
uantitative agreement was attributed to the roughness and contaminatio
n of the surfaces used in the experiments.