Collision cascades of thorium ions at 50, 100 and 150 eV in monocrystalline MgO have been investigated with the program MARLOWE which constructs the trajectory of the moving particle as a series of isolated binary collisions. Parametric study on the binding parameters has been performed to show their effect on the particle trajectories. Some computed events showed a focusing in the direction . These events are characterized by an initial energy value, energy loss in each stage of the chain and a definite number of collisions. These quantities, as calculated by MARLOWE (BCA), have been compared with the results of the hard-sphere collision approximation (HSCA).