Ramp model: Difference between revisions

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*[http://dx.doi.org/10.1103/PhysRevE.74.031108 Limei Xu, Sergey V. Buldyrev, C. Austen Angell, and H. Eugene Stanley "Thermodynamics and dynamics of the two-scale spherically symmetric Jagla ramp model of anomalous liquids", Physical Review E '''74''' 031108 (2006)]
*[http://dx.doi.org/10.1103/PhysRevE.74.031108 Limei Xu, Sergey V. Buldyrev, C. Austen Angell, and H. Eugene Stanley "Thermodynamics and dynamics of the two-scale spherically symmetric Jagla ramp model of anomalous liquids", Physical Review E '''74''' 031108 (2006)]
*[http://dx.doi.org/10.1063/1.3043665 Limei Xu, Sergey V. Buldyrev, Nicolas Giovambattista, C. Austen Angell, and H. Eugene Stanley "A monatomic system with a liquid-liquid critical point and two distinct glassy states", Journal of Chemical Physics '''130''' 054505 (2009)]
*[http://dx.doi.org/10.1063/1.3043665 Limei Xu, Sergey V. Buldyrev, Nicolas Giovambattista, C. Austen Angell, and H. Eugene Stanley "A monatomic system with a liquid-liquid critical point and two distinct glassy states", Journal of Chemical Physics '''130''' 054505 (2009)]
*[http://dx.doi.org/10.3390/ijms11125184 Limei Xu, Sergey V. Buldyrev, Nicolas Giovambattista,  and H. Eugene Stanley "Liquid-Liquid Phase Transition and Glass Transition in a Monoatomic Model", International Journal of Molecular Sciences '''11''' pp. 5184-5200 (2010)]
[[Category:models]]
[[Category:models]]
[[category:Polyamorphic systems]]
[[category:Polyamorphic systems]]

Revision as of 15:23, 4 February 2011

The ramp model, proposed by Jagla [1] and sometimes known as the Jagla model, is described by:

where is the intermolecular pair potential, , and .

Graphically, one has:

where the red line represents an attractive implementation of the model, and the green line a repulsive implementation.

Critical points

For the particular case , the liquid-vapour critical point is located at [2]:

and the liquid-liquid critical point:

Repulsive Ramp Model

In the repulsive ramp case, where , neither liquid-vapor nor liquid-liquid stable equilibria occur [2]. However, for this model a low density crystalline phase has been found. This solid phase presents re-entrant melting, i.e. this solid melts into the fluid phase as the pressure is increased.

Lattice gas version

Recently, similar behaviour has been found in a three-dimensional Repulsive Ramp Lattice Gas model [3] The system is defined on a simple cubic lattice. The interaction is that of a lattice hard sphere model with exclusion of nearest neighbours of occupied positions plus a repulsive interaction with next-to-nearest neighbours. The total potential energy of the system is then given by:

where  ; refers to all the pairs of sites that are second neighbors, and indicates the occupation of site (0 indicates an empty site, 1 indicates an occupied site).

See also

References

Related literature