Thermodynamic and dynamic anomalous behavior in the TIP4P/ε water model

Water is a fascinating molecule. Even though present
in our everyday life, it shows a number
of properties that are still not well
described. For example, most liquids contract upon cooling. This is not the case of water, a
liquid where the specific volume at ambient pressure starts to increase
when cooled below $4^C$ at atmospheric pressure. A number of models
have attempted to describe the anomalous behavior of
water. While polarizable models are time consuming
and exhibit a large number of parameters, the non polarizable
models fail in reproducing some anomalous behaviors of
water. This is the case of the dielectric constant.
In order to produce a nonpolarizable model capable of
reproducing the dielectric constant
and the solubility of the salt, a new model was developed.
We introduce the Tip4p/$\varepsilon$ model for water
and this model
is
tested for the presence of thermodynamic and dynamic
anomalies. Molecular dynamic simulations for this system
were performed and we show that for
the bulk the density versus temperature at
constant pressure exhibits a maximum.
In
addition we also show
that the diffusion coefficient versus density at constant temperature has
a maximum and a minimum. The anomalous behavior of the density
and of the diffusion coefficient obey the water hierarchy. The
results for the Tip4p-$\epsilon$ are consistent with experiments and
when compared with the Tip4p-2005 model show similar results a variety
of physical properties and better performance for the value of the dielectric constant.