The classical elastic scattering of parallel and divergent ion beams during their passage between two free atoms is studied. The problems are solved analytically for the momentum approximation and numerically by the computer simulation of ion trajectories. The expressions for the differential cross-sections of two-atomic scattering and the two-atomic focusing energyEfhave been obtained for the inverse power and Born–Mayer potentials. The regularities of two-and one-atom scattering are compared. It has been shown that the characteristics of two-and one-atom scattering are very different in the ion energy rangeE ≲ Ef. The ion beam scattering by crystal surface semichannel is discussed. It has been shown that, in this case, the ions may be consecutively focused by two atomic pairs.