The International Association for the Properties of Water and Steam has released two highly accurate formalisms, IAPWS95 and IAPWS97. The 1997 formulation, IAPWS97, uses an empirically fitted Gibbs free energy based equation of state to derive thermodynamic properties. However, with a rigid water model that does not capture the internal energy of water, we need the best fit to the experimental residual Gibbs free energy contribution of the total Gibbs free energy to parameterize our atomistic water model. Unfortunately, the residual and ideal gas contributions are not reported separately for the liquid phase region in the IAPWS97 formulation. We instead use IAPWS95 formulation which gives both the residual and the ideal gas Helmholtz free energy contributions for the liquid water regime. Similar to IAPWS97, in IAPWS95 the Helmholtz free energy based equation of state is fitted to reproduce experimentally observed water properties. Additionally, IAPWS95 is slightly more accurate than IAPWS97 as IAPWS97 was primarily designed for faster calculations and sacrifices some accuracy.