Simulations in slab geometry were carried out for three possible choices of s max , namely 1.0, All simulations were carried out in the canonical (NVT) ensemble at 298.15 K using a weakcoupling thermostat with a coupling time of 0.1 ps. The equations of motion were integrated using the modified Leap-frog scheme of Eq. ( ) with a time step of 2 fs. The full rigidity of the water molecules was maintained using three distance constraints, enforced using the modified SHAKE algorithm 101 of Suppl. Mat. Sec. 1.2, applied with a relative geometric tolerance of values). The non-bonded interactions were evaluated using charge-group truncation at a singlerange cutoff distance R c based on a pairlist updated every step. A reaction-field correction was applied with a permittivity ε RF set to 61.