The secondary MC simulations were performed under various volumes per particle. These simulations aim to assume the volume dependence of the nucleation free energy. The detailed procedure of which is much the same as the fixed-volume per particle simulation in the previous chapters. Here we explain where is different from the fixed-volume simulation in which procedure and the observed results.
We performed the MC simulations with changing number of particles N, temperature T, and volume per particle V/N: as N = 2-80, T = 0.01-1.00 ε/k, and V/N = 30, 43.2, 90, 240 and 1000 σ3. We adopted only the face-centered cubic lattice as an initial lattice of the cluster stabilization process. It is caused that, particularly in the large-N system, the stable cluster is hardly obtained if the simple cubic and the body-centered cubic were chosen as the initial lattice of the first stage. At the simulations of V/N = 43.2 σ3, we confirmed that the interaction energy and the interaction entropy of the monomer phase do not depend on the temperature, and we assumed the equilibrated values after the cluster decomposition in the phase transition calculation into the interaction energy and the interaction entropy of the monomer phase. Therefore, the monomer phase calculation was not performed at the simulations in this chapter.
In the cluster phase calculation, we restricted the configuration of the system to keep a unity cluster still high-temperature with the Stillinger's cluster criterion. However, the criterion focuses only the interparticle distance, so the shape of the cluster is not considered.[5,15] Therefore, if the configuration satisfies only a threshold value of the interparticle distance, 1.5 σ, the configuration is permitted as the cluster phase even though the configuration is collapsed and stretched by heating, like Fig. 4.2. The stretched clusters appear frequently when the number of particle becomes larger or the volume per particle larger.
|
