8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P2.62Tue 611:23-14:00Anomalous behavior in core-softened shoulder-dumbbellfluidsPaulo Netz, 1 Barbosa Marcia, 1 Juliana Paukowski, 1 Gavazzoni Cristina, 1 GonzattiGuilherme, 1 and Oliveira Alan 21 Universidade Federal do Rio Grande do Sul, Av. Bento Gonçalves 9500, 91501970,Porto Alegre, Brazil2 Universidade Federal de Ouro Preto, Ouro Preto, BrazilThe behavior of water, in particular its anomalies, has been a puzzle to researchers and has becomeeven more complicated since the discovery that some other fluids could also display waterlikeanomalies. Recently, the use of model systems with softened core pair interaction potentials incomputer simulations has been becoming a standard tool to understand the main factors behind theanomalous behavior. Among these models, the shoulder model, despite being isotropic, exhibitednot only several anomalies similar to water, but also the same hierarchy of anomalies: thermodynamicanomaly range inside the dynamical anomaly range and this last one on its turn inside thestructural anomaly range. We proposed an extension of the shoulder model, the shoulder-dumbbellmodel, introducing anisotropy in this system by building dimeric particles. Using molecular dynamicssimulations, we investigate the thermodynamics, dynamics, and structure of 250 dimers interactingby the shoulder-dumbbell core-softened potential. This system exhibits thermodynamic,dynamic, and structural anomalies somewhat enhanced when compared to the core-softened shouldermonomeric case. An orientational anomaly was also found for this system. The anisotropy dueto the dumbbell leads also to the appearance of a liquid crystal phase. We have also studied theinfluence of the parameter lambda (the distance between the centers of particles inside the dimmer)on the phase diagram. We found a surprisingly non-monotonic behavior of the anomalies onlambda: a small geometric anisotropy (small values of lambda) leads to a large enhancement ofthe anomalous regions, whereas increasingly larger values of lambda lead to the shrinking of theseregions.62