Speeding up the study of diluted dipolar systems

D.A. MARTIN; V.I. MARCONI; T.S. GRIGERA

Trieste

Otro; Spring College on the Physics of Complex Systems; 2019

ICTP

We review our results on numerical simulations of Diluted Dipolar Spheres (DDS) in the NVT ensemble, with and without [] an external field. We have performed Monte Carlo simulations, and also developed a speed-up algorithm, "Cluster Move Monte Carlo" (CMMC). Within simulations, particles tend to organize into structures. We have found and characterized several regimes. CMMC combines typical single particle rotation and translation with the movement of groups of particles, in such way that detailed balance is preserved. It is easy to implement and it speeds-up simulations by a factor 10 to 100 (compared to traditional Monte Carlo), depending on density and temperature. It is also faster than other speed-up algorithms. It is useful with truncated potentials but also when Ewald sums are used. It may be useful for other, related, on-lattice and off-lattice systems. With the aid of CMMC, se study a set of positional, orientational, and thermodynamical observables, as a function of temperature and density. We find that many of this observables change for the same values of Temperatures and densities. The study of DDS is relevant from the theoretical point of view, but can also be related to systems of technological interest, such as magnetic dipolar nanoparticles, for which, several applications have been proposed. Nowadays, nanoparticles with large dipolar moments, comparable with the ones studied here, can be synthesized. We mention briefly how our results can be related to real physical system results.