Jagla potential

Figure 2. Snapshots from computer simulations showing the coexistence between LDL and HDL in different polymorphic liquids, (a) Water. Dark and light molecules belong to LDL and HDL, respectively, (b) Silica. Dark and light spheres represent Si atoms in the HDL and LDL phase, respec tively. For clarity, 0 atoms are not shown, (c) System of particles interacting via the isotropic Jagla potential (see Fig. 8). LDL and HDL particles are both represented by dots. Lines connect pairs of particle belonging to HDL. (a), (b), and (c) are taken from Refs 33, [35], and [36], respectively.

Figure 7. Pressure dependence of the volume during the LDA-to-HDA transformation and subsequent decompression of HDA. Results are obtained from computer simulations of (a) water, using the ST2 model, and (b) a system of particles interacting via the Jagla potential (defined in Fig. 8a). At the simulated temperatures, the LDA-to-HDA transformation is not reversible, (a) and (b) are remarkable similar to tbe experimen talresultsshowninFig.6a. (a)and(b) are adapted from Refs. 67 and [63], respectively.

In order to better understand liquid polyamorphism [73,74], a systematic study was carried out on the effects of A, the ratio of characteristic energies on the existence of a LL transition, the positive or negative slope of the line of first-order LL transition in the P, T) plane, and the relationship, if any [58], between the LL transition and density anomalies. Calculations were performed in parallel for both confined and bulk water, and a spherically symmetric potential with two different length scales called the Jagla potential with both attractive and repulsive parts was used [58,64,65]. The potential is defined as... 

Using MD simulations [82,83], we studied three models, each of which has a LL critical point. Two (the TIP5P and the ST2) treat water as a multiple-site rigid body that interacts via electrostatic site-site interactions complemented by a Lennard-Jones potential. The third is the spherically symmetric two-scale Jagla potential with attractive and repulsive ramps. In all three models the loci of maxima of the relevant response functions, Ki and Cp, which coincide close to the critical point and give rise to the Widom line, were evaluated. The hypothesis that, for all three potentials, a dynamic crossover occurs when the Widom line is crossed, was carefully explored. 

Jagla, E. A. 1999. Core-softened potentials and the anomalous properties of water. Journal of Chemical Physics. Ill, 8980. 

Figure 3. Pressure versus volume isotherm at T < Tc obtained from simulations of a system of particles interacting via the Fermi-Jagla pair potential, a smooth version of the Jagla pair potential shown...

---