A comparison of the column approximation and the Howie-Basinski approach in simulations of TEM images under weak-beam diffraction conditions

Weak-beam diffraction contrast images of dislocation loops have been simulated by solving numerically the Howie-Basinski equations, which avoid the column approximation. Quantitative comparisons are made with similar simulations which do make use of the column approximation. The images predicted by the Howie-Basinski equations were displaced relative to images calculated using the column approximation, and were generally broader and somewhat lower in intensity. The differences between the images were most marked for very small loops