Thermodynamic Properties of Octamethylcyclotetrasiloxane

An equation of state for octamethylcyclotetrasiloxane is presented. The available experimental data from the literature are supplemented by new measurements on the speed of sound. Furthermore, a new force field is proposed, allowing the generation of a comprehensive thermodynamic data set by means of molecular simulation. Both the experimental and molecular simulation data are applied to develop a fundamental equation of state in terms of the Helmholtz energy. On the basis of the experimental data, the equation of state is valid from the triple-point temperature to <i>T</i> = 590 K for pressures up to <i>p</i> = 180 MPa and can be used to calculate any thermodynamic equilibrium state property. Its accuracy is assessed by a comprehensive analysis of the underlying experimental data. Finally, the range of validity was extended to <i>T</i>_max = 1200 K and <i>p</i>_max = 520 MPa by means of molecular simulation data