A parallel algorithm for Hamiltonian matrix construction in electron–molecule collision calculations: MPI-SCATCI

Abstract

Construction and diagonalization of the Hamiltonian matrix is the rate-limiting step in most low-energy electron -molecule collision calculations. Tennyson (J Phys B, 29 (1996) 1817) implemented a novel algorithm for Hamiltonian construction which took advantage of the structure of the wavefunction in such calculations. This algorithm is re-engineered to make use of modern computer architectures and the use of appropriate diagonalizers is considered. Test calculations demonstrate that significant speed-ups can be gained using multiple CPUs. This opens the way to calculations which consider higher collision energies, larger molecules and / or more target states. The methodology, which is implemented as part of the UK molecular R-matrix codes (UKRMol and UKRMol+) can also be used for studies of bound molecular Rydberg states, photoionisation and positronmolecule collisions.

UKRmol+: A suite for modelling electronic processes in molecules interacting with electrons, positrons and photons using the R-matrix method

“…This task uses an algorithm [45] especially designed to efficiently construct Hamiltonian matrices with the close-coupling structure of Eq. (21); this is carried out by either SCATCI or MPI-SCATCI [48]. The latter is a parallel implementation of a re-engineered version of the algorithm employed by SCATCI that makes use of modern computer architectures and has added functionality (see Section 6).…”

Trends in angle-resolved molecular photoelectron spectroscopy

“…The same applies to MCSCF implementations, which have been successfully developed but restricted to solving the TDSE with short pulses. 88 Besides the solution of the coupled equations for the continuum orbitals, also the evaluation of the Hamiltonian matrix elements, if a basis set is employed for the continuum, 72,89 or the reduction to the set of coupled equations, are complex and computationally demanding with complex correlated target states. This has restricted the full close-coupling approach to rather small systems.…”

UKRmol+: a suite for modelling of electronic processes in molecules interacting with electrons, positrons and photons using the R-matrix method

“…This task uses an algorithm [44] especially designed to efficiently construct Hamiltonian matrices with the close-coupling structure of Eq. (21); this is carried out by either SCATCI or MPI-SCATCI [47]. The latter is a parallel implementation of a re-engineered version of the algorithm employed by SCATCI that makes use of modern computer architectures and has added functionality (see Section 6).…”