Bidimensional fluid system with competing interactions: spontaneous and induced pattern formation

In this paper we present a study of pattern formation in bidimensional systems with competing short-range attractive and long-range repulsive interactions. The interaction parameters are chosen in such a way to analyse two different situations: the spontaneous pattern formation due to the presence of strong competing interactions on different length scales and the pattern formation as a response to an external modulating potential when the system is close to its Lifshitz point. We compare different Monte Carlo techniques showing that Parallel Tempering technique represents a promising approach to study such systems and we present detailed results for the specific heat and the structural properties. We also present random phase approximation predictions about the spontaneous pattern formation (or microphase separation), as well as linear response theory predictions about the induced pattern formation due to the presence of an external modulating field. In particular we observe that the response of our systems to external fields is much stronger compared to the response of a Lennard-Jones fluid.