‘tripleint_cc’: A program for 2-centre variational leptonic Coulomb potential matrix elements using Hylleraas-type trial functions, with a performance optimization study Original Research Article

We present a program used to calculate intricate three-particle integrals for variational calculations of solutions to the leptonic Schrödinger equation with two nuclear centres in which inter-leptonic distances (electron–electron and positron–electron) are included directly in the trial functions. The program has been used so far in calculations of image interactions and positron H2 scattering, however the precisely defined integrals are applicable to other situations. We include a summary discussion of how the program has been optimized from a ‘legacy’-type code to a more modern high-performance code with a performance improvement factor of up to 1000.