The role of the anisotropy on the solid-fluid phase transition in core-softened shoulder-dumbbells systems

Using molecular dynamics we studied the role of the anisotropy on the phase boundary of 250 dimeric particles interacting by a core-softened potential. This study led us to an unexpected result: the introduction of a rather small anisotropy, quantified by the distance between the particles inside each dimer, leads to an apparent increase of the size of the solid region in the pressure-temperature phase diagram when compared to the isotropic monomeric case. However, as the anisotropy increases beyond a threshold the solid region shrinks. We found that this behavior can be understood by the decoupling of the translational and non-translational kinetic energy components that could be interpreted as if the system would display different translational and non-translational temperatures. The phase boundaries seem to be sensitive to the translational temperature only. (C) 2014 AIP Publishing LLC.