ADDITIVITY OF GUEST AND HOST PROPERTIES IN CLATHRATES - A THERMODYNAMIC AND RAMAN-SPECTROSCOPIC INVESTIGATION OF HPTB-BASED SOLIDS

The heat capacities of hexakis(phenylthio)benzene (abbreviated as HPTB ) and the clathrate HPTB . 2CBr(4) have been determined from 30 to abo ut 300 K. In addition, the room-temperature Raman spectra have been ob tained for both compounds. The Raman spectrum of HPTB . 2CBr(4) is ver y closely approximated by the sum of the spectrum of HPTB and that of pure CBr4, indicating the additivity of the guest and host intramolecu lar interactions. These internal degrees of freedom dominate the heat capacity, and the present analysis shows the importance of the low-fre quency modes. Over a wide range of temperature below 200 K, the calcul ated Gruneisen parameter of HPTB is higher than for HPTB . 2CBr(4).