  Electronic polarization and charge transfer effects play a crucial role in
thermodynamic, structural and transport properties of room-temperature ionic
liquids (RTILs). These non-additive interactions constitute a useful tool for
tuning physical chemical behavior of RTILs. Polarization and charge transfer
generally decay as temperature increases, although their presence should be
expected over an entire condensed state temperature range. For the first time,
we use three popular pyridinium-based RTILs to investigate temperature
dependence of electronic polarization in RTILs. Atom-centered density matrix
propagation molecular dynamics, supplemented by a weak coupling to an external
bath, is used to simulate the temperature impact on system properties. We show
that, quite surprisingly, non-additivity in the cation-anion interactions
changes negligibly between 300 and 900 K, while the average dipole moment
increases due to thermal fluctuations of geometries. Our results contribute to
the fundamental understanding of electronic effects in the condensed phase of
ionic systems and foster progress in physical chemistry and engineering.
