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

Modeling 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 purposes, 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.