  Many important processes affecting the Earth's climate are determined by the
physical properties of seawater. Desalination of seawater is a significant
source of drinking wate.Since the physical properties of seawater governing
these processes depend on the molecular interactions among its components, a
deeper knowledge of seawater at the molecular level is needed. However MD
studies reporting the physical properties of seawater are currently lacking.
This is probably due to the usual perception of the seawater composition being
too complex to approach.This point of view ignores the fact that physical
properties of seawater are dependent on a single parameter representing the
composition, namely the salinity. This is because the relative proportions of
any two major constituents of seasalt are always the same. An obstacle to
performing MD simulations of seawater could have been the unavailability of a
satisfactory force field representing the interactions between water molecules
and dissolved substances. This drawback has recently been overcome with the
proposal of the Madrid-2019 FF.Here we show for the first time that MD
simulations of seawater are feasible. We have performed MD simulations of a
system, the composition of which is close to the average composition of
standard seawater and with the molecular interactions given by the Madrid-2019
force field. We are able to provide quantitative or semiquantitative
predictions for a number of relevant physical properties of seawater for
temperatures and salinities from the oceanographic range to those relevant to
desalination processes. The computed magnitudes include static (density),
dynamical (viscosity and diffusion coefficients), structural (ionic hydration,
ion-ion distribution functions) and interfacial (surface tension) properties.
