MONTE-CARLO SIMULATION OF ION-BEAM CHANNELING IN YBA2CU3O7

A Monte Carlo program (UPIC) for the simulation of ion channeling in c rystals with complex structure is described. The program is applied to simulate the channeling of 1.5 MeV He+ and 1 MeV D+ near the [001] ax is of YBa2CU3O7 assuming strongly correlated atomic displacements alon g the [001] Cu-O rows in the superconducting state. The values for the abrupt change in the half-width of the channeling dip observed in exp eriments [R.P. Sharma et al., Phys. Rev. B 38 (1988) 9287] at the temp erature of the superconducting transition, T-c, are reproduced in the simulations with correlation coefficients of 0.8-0.9. The increase in the minimum channeling yield at T-c found in measurements [T. Haga et al., Phys. Rev. B 41 (1990) 826] can be qualitatively explained by the increase in dechanneling rate due to correlations.