  We present our experience of porting the code used in the wave-packet
convergent-close-coupling (WP-CCC) approach to run on NVIDIA V100 and AMD
MI250X GPUs. The WP-CCC approach is a method used in the field of ion-atom
collision physics to describe various processes such as elastic scattering,
target excitation and electron-capture by the projectile. It has demonstrated
its effectiveness in modelling collisions involving proton or bare ion
projectiles with various atomic and molecular targets, especially those which
can be considered as one or two-electron systems. Such calculations find their
application in computational atomic physics as well as in the modelling of
fusion plasmas and in hadron therapy for cancer treatment. The main
computational cost of the method lies in the solution of an emerging set of
coupled first-order differential equations. This involves implementing the
standard Runge-Kutta method while varying the projectile position along
multiple straight-line paths. At each projectile position several millions of
matrix elements need to be calculated which is accomplished using the OpenACC
programming model. Once these matrix elements are computed, the subsequent
steps involve matrix inversion and multiplication with another matrix. To
expedite these operations, a GPU-accelerated LAPACK routine, specialised for
solving systems of linear equations, is employed. For AMD GPUs, this routine is
accessible through the hipSOLVER library, while for NVIDIA GPUs, it can be
obtained from the cuSOLVER library. The portability, performance and energy
efficiency of the CPU-only code have been compared with the GPU-accelerated
version running on AMD and NVIDIA GPUs. The implementation of GPU-accelerated
WP-CCC code opens up avenues for exploring more sophisticated collision
processes involving complex projectile and target structures, which were
previously considered infeasible.
