Conclusions
The impact produced by the evolution of computer technologies towards Grid systems on the size and the complexity of the problems that theoretical and computational studies of chemical reactions can afford is discussed. The analysis is extended on one side to how this affects the way computer codes are structured to gain significant efficiency and on the opposite side to how alternative formulation of the reactive scattering equations can be written to exploit the advantages of concurrent computing. In particular, the use of traditional low level parallelization libraries has been considered and compared with that of coordination languages based on skeletons and related extensions. As for alternative approaches those based on BO coordinates which have the advantage of formulating in a homogeneous way the potential and the Laplacian operator, are analyzed. In particular new formulations of the functional representations of the interaction are discussed and the formulation of the Hamiltonian in terms of both BO and HYBO coordinates are given.