  The mechanical behavior in compression of [111] LiF micropillars with
diameters in the range 0.5 $\mu$m to 2.0 $\mu$m was analyzed by means of
discrete dislocation dynamics at ambient and elevated temperature. The
dislocation velocity was obtained from the Peach-Koehler force acting on the
dislocation segments from a thermally-activated model that accounted for the
influence of temperature on the lattice resistance. A size effect of the type
"smaller is stronger" was predicted by the simulations, which was in
quantitative agreement with previous experimental results by the authors
\cite{SWC14}. The contribution of the different physical deformation mechanisms
to the size effect (namely, nucleation of dislocations, dislocation exhaustion
and forest hardening) could be ascertained from the simulations and the
dominant deformation mode could be assessed as a function of the specimen size
and temperature. These results shed light into the complex interaction among
size, lattice resistance and dislocation mobility in the mechanical behavior of
$\mu$m-sized single crystals.
