  We report molecular dynamics simulation of the (overall neutral) system
consisting of an immobile macroion surrounded by the electrolyte of multivalent
counterions and monovalent coions. As expected theoretically, counterions
adsorb on the macroion surface in the amount much exceeding neutralization
requirement, thus effectively inverting the sign of the macroion charge. We
find two conditions necessary for charge inversion, namely, counterions must be
multivalently charged and Coulomb interactions must be strong enough compared
to thermal energy. On the other hand, coion condensation on the multivalent
counterions similar to Bjerrum pairing is the major factor restricting the
amount of charge inversion. Depending on parameters, we observe inverted charge
up to about 200% the original charge of the macroion in absolute value. Our
findings are consistent with the theory of "giant charge inversion"
[Phys.Rev.Lett., v. 85, 1568 (2000)].
