No abstract

A three dimensional version of the electro-elastic model allowing the description of spin-crossover (SCO) materials taking into account for the volume change at the transition between the LS and the HS spin states is developed. The investigations are realized on a rectangular parallelepiped lattice with a cubic symmetry. The SCO units are modeled by two-states fictitious spins coupled by springs whose equilibrium distances depend on the spin states. We implemented massive parallel simulations using CUDA (Compute Unified Device Architecture) programming where the spin states are updated using Monte Carlo Metropolis algorithm while the mechanical relaxation (lattice position) is performed by molecular dynamics. In this work, we investigated: (i) the case of the thermal spin transition showing the macroscopic deformation of the parallelepiped accompanying the propagation of single domains, and (ii) the isothermal relaxation of the photoinduced metastable HS fraction at low temperature. In both cases, the interplay between the electronic and the structural aspects of these transformations is analyzed and discussed in relation with the model parameters.