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Thermodynamic Properties of Ferrocene Crystal

1981; Volume: 71; Issue: 3-4 Linguagem: Inglês

10.1080/00268948108072321

0026-8941

Kouji Ogasahara, Michio Sorai, Hiroshi Suga,

Advanced Chemical Physics Studies

Abstract The heart capacities of ferrocene crystals have been measured between 13 and 300 K for large and powdered crystals. The phases studied include the triclinic metastable low-tempreature (LT) phase, the monoclinic high-temperatture (HT) phase, the orthorhombic stable LT-phase and also the undercoled HT-and the superheated orthorhombic LT-phases. The enthalpy and entropy of the A-type transition from the metastable LT-to the undercooled HT-phase at 163.9 K and the first order transition from the stable LT-to the HT-phase at 242 have been determned. The latter phase transition is concluded to be characterized by softening of a translational mode along the crystallographic "c-axis." The influence of crystal size is reflected in the shape of the heat capacity curve in the vicinity of the A-point whereas the transition enthaply and entropy are identical regardless of crystal size. The disintegration phenomenon of large ferrocene crystal may be interprented in terms of a change in the state on a P-H-T surface.