Inelastic scattering of electrons in water from first principles: cross sections and inelastic mean free path for use in Monte Carlo track-structure simulations of biological damage

Abstract

Modelling the inelastic scattering of electrons in water is fundamental, given their crucial role in biological damage. In Monte Carlo track-structure (MC-TS) codes used to assess biological damage, the energy loss function (ELF), from which cross sections are extracted, is derived from different semi-empirical optical models. Only recently have first ab initio results for the ELF and cross sections in water become available. For benchmarking purpose, in this work, we present ab initio linear-response time-dependent density functional theory calculations of the ELF of liquid water. We calculated the inelastic scattering cross sections, inelastic mean free paths, and electronic stopping power and compared our results with recent calculations and experimental data showing a good agreement. In addition, we provide an in-depth analysis of the contributions of different molecular orbitals, species and orbital angular momenta to the total ELF. Moreover, we present single-differential cross sections computed for each molecular orbital channel, which should prove useful for MC-TS simulations.

Energy Deposition around Swift Carbon-Ion Tracks in Liquid Water

“…is remarkable, and better than the MELF-GOS predictions, which slightly overestimate the experimental ELF at large momenta. Noteworthy, current results are closer to the experimental data than similar LR-TDDFT calculations recently reported [ 87 ].…”

“…Using the point to sample the first Brillouin zone and a (kinetic) energy cut-off of 130 Ry, the self consistent DFT convergence is reached within the energy error of . It should be noted that, even though a recent study optimised liquid water samples by ab initio molecular dynamics [ 87 ], the current approach can be considered for all practical purposes equivalent (which will be seen from the results in the coming paragraphs), as our final classical molecular dynamics was also optimised by first principles prior to the ELF calculation.…”

Nonlinear electronic stopping of negatively-charged particles in liquid water

“…The LR-TDDFT result also presented in Fig. 2(a) is obtained from the ab initio energy loss function [40]. The position of the Bragg peak is significantly different.…”

“…The agreement between our results and Bin Gu et al [19] for H + is very reasonable although, at low proton velocities, our ESP is slightly lower than the reference result. The discrepancy may be associated with the differences in the pseudopotentials and basis sets used in our Siesta calculations, versus the ones used with the (dotted line) and with the LR-TDDFT stopping power [40] (dashed line). The semi-empirical data points from Muñoz et al [41] are obtained by converting the mass stopping power for gas phase to ESP by assuming the density of 1 g/cm 3 .…”

“…ESTAR data [23] (thin solid line, on the most right) and Ashley et al [42] also based on dielectric response (thin dashed line) are also presented for comparison. (b) Comparison of ESP obtained from RT-TDDFT (full symbols) and from LR-TDDFT using the mass-dependent integration limits for q (see [40]) (solid line) and without such limits (dashed line). See text for explanation.…”