Fluctuation-based computer calculation of partial molar properties. I. Molecular dynamics simulation of constant volume fluctuations

Partial molar volumes, energies, and enthalpies are calculated via the (N,U,V) molecular dynamics implementation of their corresponding operational definitions in terms of constant volume fluctuations. The method is exact for the former property but only approximate for the latter two. The partial molar volume operational definition satisfies Euler's homogeneous function theorem identically. The corresponding energy definition is based upon a differential equation and does not, therefore, satisfy the homogeneity constraint identically. A numerically unimportant but conceptually profound correction to the recently derived partial molar energy operational definition is incorporated and its theoretical implications discussed.