Communication: Phase diagram of C{sub 36} by atomistic molecular dynamics and thermodynamic integration through coexistence regions
- Dipartimento di Fisica e di Scienze della Terra, Università degli Studi di Messina and CNISM (Consorzio Nazionale Interuniversitario di Struttura della Materia) Viale F. Stagno d'Alcontres 31, 98166 Messina (Italy)
We report an atomistic molecular dynamics determination of the phase diagram of a rigid-cage model of C{sub 36}. We first show that free energies obtained via thermodynamic integrations along isotherms displaying “van der Waals loops,” are fully reproduced by those obtained via isothermal-isochoric integration encompassing only stable states. We find that a similar result also holds for isochoric paths crossing van der Waals regions of the isotherms, and for integrations extending to rather high densities where liquid-solid coexistence can be expected to occur. On such a basis we are able to map the whole phase diagram of C{sub 36}, with resulting triple point and critical temperatures about 1770 K and 2370 K, respectively. We thus predict a 600 K window of existence of a stable liquid phase. Also, at the triple point density, we find that the structural functions and the diffusion coefficient maintain a liquid-like character down to 1400–1300 K, this indicating a wide region of possible supercooling. We discuss why all these features might render possible the observation of the melting of C{sub 36} fullerite and of its liquid state, at variance with what previously experienced for C{sub 60}.
- OSTI ID:
- 22419850
- Journal Information:
- Journal of Chemical Physics, Vol. 141, Issue 9; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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