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 T = 590 K for pressures up to p = 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 Tmax = 1200 K and pmax = 520 MPa by means of molecular simulation
data.