On the validity of the column approximation in electron microscopy

Abstract The authors develop a theory very slightly different from that of Takagi in the non-column case. They get numerical results in the case of 100 kev electron energy with a single edge dislocation and dislocation dipole close to the upper surface. Discrepancies between the column approximation and the non-column case are very small in the general case. If the Bragg angle becomes very large (≳4°) discrepancies may be important.