  Solid-density plasmas driven by intense x-ray free-electron laser (XFEL)
radiation are seeded by sources of non-thermal photoelectrons and Auger
electrons that ionize and heat the target via collisions. Simulation codes that
are commonly used to model such plasmas, such as collisional-radiative (CR)
codes, typically assume a Maxwellian distribution and thus instantaneous
thermalization of the source electrons. In this study, we present a detailed
description and initial applications of a collisional particle-in-cell code,
PICLS, that has been extended with a self-consistent radiation transport model
and Monte-Carlo models for photoionization and KLL Auger ionization, enabling
the fully kinetic simulation of XFEL-driven plasmas. The code is used to
simulate two experiments previously performed at the Linac Coherent Light
Source investigating XFEL-driven solid-density Al plasmas. It is shown that
PICLS-simulated pulse transmissions using the Ecker-Kr\"oll continuum-lowering
model agree much better with measurements than do simulations using the
Stewart-Pyatt model. Good quantitative agreement is also found between the
time-dependent PICLS results and those of analogous simulations by the CR code
SCFLY, which was used in the analysis of the experiments to accurately
reproduce the observed K{\alpha} emissions and pulse transmissions. Finally, it
is shown that the effects of the non-thermal electrons are negligible for the
conditions of the particular experiments under investigation.
