Solid{endash}fluid equilibrium for a molecular model with short ranged directional forces
- Departamento de Quimica Fisica, Facultad de Ciencias Quimicas, Universidad Complutense, 28040 Madrid (Spain)
- Department of Chemical Engineering, University of Massachusetts, Amherst, Massachusetts 01003 (United States)
The phase diagram of a system of hard spheres with short-range tetrahedral association has been determined by computer simulation and theory. The fluid phase and two solid phases were considered. One of these solid phases is a low-density solid closely related in structure to ice Ic and the other is a high-density solid closely related in structure to ice VII. At high temperatures freezing occurs into the high-density solid whereas at low temperatures freezing occurs into the low-density solid. At an intermediate temperature a triple point is found where the fluid coexists with the two solids simultaneously. Although the low-density solid melts to a high-density fluid, this transition is found to be metastable with respect to the transformation into a high-density solid. This is evidence that short-range tetrahedral attractive forces are not in and of themselves sufficient to explain the anomalous melting of water. Our results indicate that vapor{endash}liquid equilibrium for the model is preempted by solidification. Monte Carlo simulation results for the fluid phase are described successfully by Wertheim{close_quote}s theory whereas those of the solid phases are described qualitatively by the cell theory. {copyright} {ital 1998 American Institute of Physics.}
- OSTI ID:
- 670188
- Journal Information:
- Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 22 Vol. 109; ISSN JCPSA6; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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