Properties of Neat Water Systems

We examine here some of the more important aspects of pure water systems that have been used either to fit or to gauge models. Two types of information can be used for these purposes. The first type is experimental 

The internal energy is the average of the potential energy of a sample of molecules. 

The sum is over all pairs of molecules the angle bracket notation as usual denotes an ensemble average of the enclosed quantity, and )(r y) is the potential of interaction between molecules i and /. The p term is the energy associated with induced moments (polarization). It is treated in many ways, including setting it to zero the nontrivial treatments are discussed in later sections. The pressure, p, is obtained using the molecular virial formulation  

Accurate determinations of Dg can be realized, provided the long-time region is reached where R t) is linear in time. Alternatively, the equivalent expression 

The dielectric constant 32 jg property that is sometimes used to gauge the quality of a potential function, but it is not used to determine potential parameters because simulation times on the order of nanoseconds are needed for good convergence. The dielectric constant is obtained from the expression  

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