In the present work, numerical simulations for spin-crossover 1D nanoparticles embedded in a matrix are presented and discussed in the framework of an Ising-like model that takes into account short- (J) and long-range (G) interactions as well as the interactions (L) between the surface molecules and the surroundings. For a new algorithm, detailed in this contribution, to calculate the density of states for each macro state, we obtained three-state thermal behaviour for some sets of parameters. We analyze the effects of these different parameters as well as the number of 1D SCO molecules on this particular behaviour.