Fast Algorithm for Diluted Dipolar Systems with and without External Field

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

Bueno Aires

Congreso; Stat Phys 27 ( International Conference on Statistical Physics); 2019

Fast Algorithm for Diluted Dipolar Systems with and without External Field. Authors: D. A. Martin (1), T. S. Grigera (2,3), and V. I. Marconi (4). Affiliations:    (1) Instituto de Investigaciones Físicas de Mar del Plata (IFIMAR), CONICET and Universidad Nacional de Mar del Plata, Funes no. 3350, 7600, Mar del Plata, Argentina(2) Instituto de Física de Líquidos y Sistemas Biológicos (IFLYSIB), CONICET and Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Calle 59 no. 789, B1900BTE La Plata, Argentina(3) CCT CONICET La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina(4) FaMAF and IFEG (UNC-CONICET), Universidad Nacional de Córdoba, X5000HUA Córdoba, Argentina  Abstract: 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. Without external filed, we draw a regime diagram including simple-fluid, chain-fluid, ring-fluid, gel, and antiparallel columnar regimes. We later study how regime diagram changes in the presence of an external field. 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.