Comparison of average-potential models and binary-collision models of axial channeling and blocking

A comparison is made of three types of calculations of the axial "channeling dip": the large decrease in yield of close-encounter processes for energetic ions incident on a single crystal parallel to a low-index direction. The models, indicated as (1) the binary-collision model, (2) the halfway-plane model, and (3) the continuum model, are used to calculate the dip for two standard cases corresponding to recent experiments. The methods are compared as to treatment of potential and treatment of thermal vibrations. The ease of calculation versus quantitative accuracy for the different methods is discussed, and finally the agreement with experimental results is briefly reviewed.