Shape effects on the cluster spreading process of spin-crossover compounds analyzed within an elastic model with Eden and Kawasaki dynamics
Résumé
In this paper we study the growth properties of domains of low-spin molecules in a high-spin background in open-boundary elliptically shaped spin-crossover systems within the framework of a mechanoelastic model. The molecules are situated on a triangular lattice and are linked by springs, through which they interact. Elliptical shapes are chosen in order to allow an in-depth analysis of cluster shapes as a function of the local curvature at their starting point and the length of the interface between the two phases. In contrast to the case of rectangular and hexagonal shapes, where the clusters always start from corners, we find that for ellipses clusters nucleate from vertices, covertices, or any other site. We apply and compare two kinds of dynamics, Eden-like and Kawasaki, in order to determine the stable shape of the clusters and the most probable starting points. We show that the wetting angle for small clusters is somewhat higher than π/2 and approaches this value only for large clusters. The stability of clusters is analyzed by comparing the Gibbs free energy to the elastic energy in the system and is discussed as a function of the cluster size, curvature of the starting place, and temperature.