Hydrofluoroolefins (HFO) are considered as the fourth generation of working fluids as they exhibit a low Global Warming Potential, though at the moment, only a few members of the HFO family are commercialized. For most HFO compounds, experimental data for their thermophysical properties are rare, which hampers the exploration of their performance in technical applications. In our earlier work [Raabe, G.; Maginn, E. J. J. Phys. Chem. B 2010, 114, 10133-10142; Raabe, G. J. Phys. Chem. B 2012, 116, 5744-57511 we have introduced a transferable force field for fluoropropenes, which enables reliable predictions of their thermophysical properties by molecular simulations. In this work, we apply the force field model for simulation studies on the VLE of the hexafluorobutenes cis- and trans-HFO-1336mzz. We additionally present an extension of the force field to the chlorinated compounds cis- and trans-HCFO-1233zd, and provide molecular simulation results for the VLE properties of both isomers. As both trans-1233zd and cis-1336mzz are discussed as working fluids for low grade Organic Rankine Cycles (ORC), we also compare their predicted thermophysical properties with those of the widely used ORC-working fluid R-245fa.