If a bulk crystal is cut, then the surface atoms often "reconstruct", or shift from their bulk equilibrium positions. Therefore X-rays diffracted from the surface will have their Bragg reflections at different angles. Unfortunately, the volume of the surface region is much less than that of the bulk crystal resulting in much less intense diffraction spots. Hence a synchrotron X-ray source is needed in order to acquire the data in a reasonable time. The diffracted X-rays provide information on the surface reconstructions and is complementary to LEED.