Theoretical Characterization of the Minimum-Energy Structure of (SF6)2

Thermodynamic Properties of van der Waals Dimers and Trimers of Nonpolar Gases and Their Correlation with Lennard-Jones Potential Well Depths

A method of unifying the equilibrium thermodynamic properties ΔH^o and ΔG^o relating to the van der Waals dimers and trimers of 15 nonpolar gases (He-Xe, H₂, D₂, CH₄, CF₄, ethene, ethane, CO₂, SF₆, propane, and neopentane) is described. Values of ΔH^o and ΔG^o, obtained at the reduced temperature T_r = 0.7, show good correlation with the respective Lennard-Jones pair potential well depth, calculated from the monomer critical temperature and the acentric factor. Such relationships present the opportunity to estimate the van der Waals dimer and trimer thermodynamic properties of other nonpolar molecules, and examples of seven such applications are given. It is found that the enthalpies of dimerization and trimerization of the 15 gases are about 21 and 29% of the respective condensation enthalpies, providing information about the thermodynamics of small clusters in relation to liquefaction.

Conformational landscape of the SF6 dimer as revealed by high resolution infrared spectroscopy and complexation with rare gas atoms

The rovibrational spectrum of the SF₆ dimer in the ν₃ mode region has been revisited at high resolution with a tunable quantum cascade laser spectrometer coupled to a pulsed pin hole or slit supersonic expansion. Among the three features observed, two of them are assigned to conformation of the SF6 dimer, clearly distinguished by their different S–S distances, and the third one to a (SF₆)₂–He complex.