Effective potential of plane channeling in LiH crystal

The problem on determining the effective potentials of channeling along the charged planes (111) and (11-bar1) in the LiH finite crystal is considered. The criteria of the applicability of the formulae in the case of the infinite crystal are obtained. The estimate of the crystal surface layer value, wherein these formulae are not applicable, is given. In the case, when the crystal dimensions along the z-axis are much smaller, than the particle flight time, then the finite crystal potential behaves inside the crystal similarly to the infinite crystal potential