UK Molecular R-Matrix (UKRmol+)

UKRmol+ is an implementation of the time-independent R-matrix method for molecules. The suite determines scattering data (e.g. integral cross sections, resonance parameters, vibrational excitation cross sections for diatomic molecules) for low energy electron and positron collisions, photoionization observables, and permanent and transition dipole moments between bound and continuum states that can be used to model further photon-induced processes, for example, by means of the R-matrix with time approach and software.

UKRmol+ requires external quantum chemistry codes (e.g. Molpro) to provide target molecular orbitals used to build multi-configurational, multicentric wavefunctions. Gaussian and/or B-spline basis functions are used to represent the continuum; all integral operations (evaluation, transformation, etc.) in the mixed basis are carried out using the GBTOlib, a high-performance library for evaluation of molecular integrals.

The suite contains about a dozen programs, some serial, some multi-threaded, and some employing MPI. The source codes together with CMake scripts for the configuration, compilation, testing and installation of the suite are freely available as a tarball from Zenodo.