We subsequently carried out an MD simulation to recrystallize the particle obtained from the GCMC simulations. To this end, we performed a simulated thermal annealing procedure where we first heated the particle to 2000 K at a rate of 80 K ps -1 , maintained the temperature for 75 ps, and then slowly cooled the system down to 1 K at a rate of 16 K ps -1 , as shown in Figure . The maximum temperature of 2000 K allowed for ample but non-destructive mobility of atoms in the particle. At even higher temperatures, within the simulation time evaporation of small MgO clusters (about ten atoms) was observed and the nanoparticle became unstable. The recrystallization process took place between 25 ps and 100 ps at 2000 K, which is signified by a decrease of the relative energy in Figure . While the kinetic energy of the system remains constant in this range (temperature = kinetic energy), the potential energy decreases due to the rearrangement process. The final structure of the MgO particle becomes visible after the cooling phase is completed. The particle has assumed rocksalt structure and the initially round particle now has a cubic shape. In simulations with smaller periods than 75 ps at 2000 K, the recrystallization process was not yet complete and grain boundaries were present in the particle, even though the rocksalt phase was already clearly apparent.