  Confronting grand canonical titration Monte Carlo simulations (MC) with
recently published titration and charge reversal (CR) experiments on silica
surfaces by Dove et al. and van der Heyden it et al, we show that ion-ion
correlations quantitatively explain why divalent counterions strongly promote
surface charge which, in turn, eventually causes a charge reversal (CR).
Titration and CR results from simulations and experiments are in excellent
agreement without any fitting parameters. This is the first unambiguous
evidence that ion-ion correlations are instrumental in the creation of highly
charged surfaces and responsible for their CR. Finally, we show that charge
correlations result in "anomalous" charge regulation in strongly coupled
conditions in qualitative desagreement with its classical treatment.
