A Monte Carlo study of the effects of temperature and of wall separation on the structure and properties of water between metal walls

Monte Carlo simulations of water between metallic(copper) plates ca. 41 Å apart at 298 and 333 K have been carried out using the ST2 model for water, representing the metal–water interactions by Lennard-Jones and electrostatic image forces. Oscillations in the singlet density functions largely, but not completely, die out at the middle of the box. In comparison with previous runs at 298 K using a shorter box (ca. 23 Å) but the same density, little change is found in the pair distributions functions and only a fairly small change in the surface potential. In agreement with a previous suggestion, clear evidence is found that the surface potential is much higher at the higher temperature. The effect of a change in density of ca. 20% is presented for a shorter box. Much of the lack of symmetry about the middle of the box present in an earlier run at normal density is thereby removed, and an increase in surface potential from ca. 0.36 to ca. 0.49 V is observed.