Software for scientific simulations

Several codes developed by Action participants are available through the AMOS Gateway, A Portal for Research and Education in Atomic, Molecular, and Optical Science:

Some of them are:

R-Matrix with Time Dependence (RMT)

RMT is a programme which solves the time-dependent Schrödinger equation for general, multielectron atoms, ions and molecules interacting with laser light. As such it can be used to model ionization (single-photon, multiphoton and strong-field), recollision (high-harmonic generation, strong-field rescattering) and, more generally, absorption or scattering processes with a full account of the multielectron correlation effects in a time-dependent manner. Calculations can be performed for targets interacting with ultrashort, intense laser pulses of long wavelength and arbitrary polarization. Calculations for atoms can optionally include the Breit–Pauli correction terms for the description of relativistic (in particular, spin–orbit) effects.The code is written in Fortran, and invokes both distributed and shared memory parallelism via MPI and OpenMP.

License: GNU General Public License 3

Acknowledgements: RMT is part of the UK-AMOR suite, and can be obtained for free from The development of RMT has benefited from computational support from CoSeC, the Computational Science Centre for Research Communities, through CCPQ. Funding from the EPSRC under Grants No. EP/P022146/1, No. EP/P013953/1, No. EP/R029342/1, and No. EP/T019530/1.


Time-dependent Recursive IndeXing (TRECX)

The time-dependent Recursive indeXing method for strong-field interactions with atoms and molecules. tRecX is a C++ code for solving generalized inhomogeneous time-dependent Schrödinger-type equations idΨ /dt = H[t, Ψ ] + Φ in arbitrary dimensions and in a variety of coordinate systems. The operator H[t, Ψ] may have simple non-linearities, as in Gross-Pitaevskii and Hartree(-Fock) problems.

Primary application of tRecX has been for non-perturbative strong-field single and double photo-electron emission in atomic and molecular physics. The code is designed for large-scale ab initio calculations, for exploring models, and for advanced teaching in computational physics.

License: GNU General Public License 2


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.

  • Main Developers: Zdeněk Mašín, Jakub Benda, Jimena D. Gorfinkiel, Jonathan Tennyson, Alex G. Harvey and many colleagues who have contributed to the development of the UK Molecular R-matrix codes over many years
  • The code is written in Fortran 95 with use of some Fortran 2003 features and uses OpenMP and optionally MPI.
  • Contact:
  • Source code
  • CPC UKRmol+ paper
  • Performance
  • Examples from the NIST AMPGateway Workshop, December 2019
  • Further information



XChem is a solution for an all-electron ab-initio calculation of the electronic continuum of molecular systems. XChem combines the tools of quantum chemistry (as implemented in Molcas) and scattering theory to accurately account for electron correlation in the single-ionization continuum of atoms, small and medium-size molecules.

  • Developers: C. Marante, M. Klinker, L. Argenti, V. Borrás, I. Corral, J. González-Vázquez and F. Martín.
  • XChem website
  • Performance