| Method |
Researchers studied the hydration shells of H3O+ at temperatures ranging from 260 to 340 K using the multi-state empirical valence-bond methodology (MS-EVB2). Researchers have run second-generation MS-EVB20 trajectories for
216 water molecules plus a single proton in a 18.64 Å-wide
cube (corresponding to a density ?=1.0 g/cm3 at 300 K) with
periodic boundary conditions and Ewald summation, at several
temperatures (T) between 260 and 340 K. Each trajectory was
first equilibrated (NVT ensemble) for about 100 ps and then
run (with 0.5 fs time steps) without the thermostat (NVE
ensemble) for 250 ps, saving the atomic coordinates every 25
fs. At each temperature several (3-10) such trajectories were
generated (with different initial conditions), producing up to
100,000 time frames constituting the sample space for the
statistics reported below. For each frame, the hydronium oxygen
was identified as the one with the three closest hydrogen atoms,
and its first two solvation shells were constructed by a nearest neighbor
search algorithm (see Figure 1). Water molecules not
forming hydrogen bonds to these shells were defined as “bulk water”. |