Phase Transitions and Coexistence in Nanoclusters of KCl

Phase Transitions

These simulations were conducted by the control of temperature (see the Introduction on the procedure meaning and expected phase diagrams profiles).
For each nanocluster (with 8, 64, 216 and 512 ions) two types of calculations were performed: slow heating and slow cooling.
Additionally, the clusters with 216 and 512 ions were subjected to fast cooling from the liquid in order to detect glass-like structures. Afterwards, a slow heating was performed on them to observe their annealing towards crystal-like structures.

It is noteworthy that the number of ions is not "magic". Indeed, KCl crystallizes in a faced-centred cubic (f.c.c.) lattice. So, considering the translation of the unit cell, with two ions (K⁺ and Cl^-), through the three-dimensional space, one should find the right number of ions from (2xn)³, where n is the number of unit cells per dimension.

The figures below show the evolution of the configurational and total energy, and other properties, as functions of  temperature, for the clusters with 64 and 512 ions. The table guides the reader to computer animations for different cluster sizes and processes. Details of the simulations are described in:

Phase Transitions in Ionic Clusters, F.Fernandes; L.Neves, American Institute of Physics Conference Proceedings (F. Bernardi, J.L. Rivail, Eds), 330 (1995) 313-318.

Figure 1. Melting and freezing by slow heating and

cooling

Figure 4. m.s.d. before and after freezing

Figure 2. r.d.f. before melting

Figure 3. r.d.f. after melting

Figure 5. Snapshot at the freezing line end (~2K)

Figure 6. Melting and freezing by slow heating and cooling,
             and glass formation by fast cooling

Crystal at ~100 K, after slow cooling from the liquid

Glass at ~100 K, after fast cooling from the liquid