VOLSCAT2.0: The new version of the package for electron and positron scattering off molecular targets

VOLSCAT is a computer program which implements the Single Center Expansion (SCE) method to solve the scattering equation for the elastic collision of electrons/positrons off molecular targets. The scattering potential needed is calculated by on-the-fly calls to the external SCELib library for molecular properties, recently ported to GPU (Graphic Processing Unit) computing environment, and made available by means of an Application Program Interface (SCELib-API) which is also provided with the VOLSCAT package in a beta version. We here announce the new release 2.0 which presents additional features with respect to the previous version aiming at a significant enhancement of its capabilities to deal with larger molecular systems. In VOLSCAT 2.0 we implemented a new method for the calculation of resonances width and position based on the theory of the Time-Delay Matrix (TDM) analysis aimed at improving the spectra resolution when dealing with several overlapping resonances. As implemented in VOLSCAT 2.0 the TDM analysis typically results more efficient as higher is the molecular symmetry thus an extended Breit-Wigner analysis of the computed partial resonances has also been included in the code. Now the end-user can couple both methods of resonance analysis and shed light on their behaviour by dumping cross sections and eigenphases with respect to projectile energy at a level as deep as a single partial wave. Furthermore, the new version of VOLSCAT has been now fully ported on the Message Passing Interface standard and linear algebra operations are now based on CUDA and MAGMA libraries. As such, VOLSCAT 2.0 is able to exploit at best the most recent distributed computing architecture based on hybrid nodes with an efficient method of workload balancing. The result is a high throughput approach to the solution of complex e(-)/e(+)-molecule scattering problems finally making feasible the study of larger molecular systems with respect to past versions of the code. (C) 2018 Published by Elsevier B.V.