  Realistic modeling of ionic systems necessitates taking explicitly account of
many-body effects. In molecular dynamics simulations, it is possible to
introduce explicitly these effects through the use of additional degrees of
freedom. Here we present two models: The first one only includes dipole
polarization effect, while the second also accounts for quadrupole polarization
as well as the effects of compression and deformation of an ion by its
immediate coordination environment. All the parameters involved in these models
are extracted from first-principles density functional theory calculations.
This step is routinely done through an extended force-matching procedure, which
has proven to be very succesfull for molten oxides and molten fluorides. Recent
developments based on the use of localized orbitals can be used to complement
the force-matching procedure by allowing for the direct calculations of several
parameters such as the individual polarizabilities.
