Structural anomalies for a three dimensional isotropic core-softened potential

Abstract

Using molecular dynamics simulations we investigate the structure of a system of particles interacting through a continuous core-softened interparticle potential. We found for the translational order parameter t a local maximum at a density rho(t-max) and a local minimum at rho(t-min)>rho(t-max). Between rho(t-max) and rho(t-min), the t parameter anomalously decreases upon increasing pressure. For the orientational order parameter Q(6) a maximum was observed at a density rho(t-max)<rho(Qmax)<rho(t-min). For densities between rho(Qmax) and rho(t-min), both the translational (t) and orientational (Q(6)) order parameters have anomalous behavior. We know that this system also exhibits density and diffusion anomalies. We found that the region in the pressure-temperature phase diagram of the structural anomaly englobes the region of the diffusion anomaly that is larger than the region limited by the temperature of maximum density. This cascade of anomalies (structural, dynamic, and thermodynamic) for our model has the same hierarchy as that observed for the simple point charge/extended water.

Quasibinary amorphous phase in a three-dimensional system of particles with repulsive-shoulder interactions

“…Analogous behavior has been demonstrated for a similar model. 23 The behavior that we observe in this three-dimensional ͑3D͒ system bears some striking similarities to that observed in two-dimensional system with "repulsive-shoulder" …”

Anomalies in a waterlike model confined between plates

“…In these cases, the diffusion coefficient has a region in which it grows with density representing the density anomalous region. The temperature of maximum and minimum diffusion coefficient are lower in the confined system than in the bulk case 69 . Our finding are in agreement with the observations of the diffusion coefficient in coarse-grained model confined between smooth hydrophobic plates, separated at 0.5nm 38 and atomistic models 23 .…”

“…The pressure versus temperature phase diagram of this system in the bulk was studied by Oliveira et al 68,69 . They found that a system or particles interacting through this potential exhibits a region in the pressure-temperature phase diagram where the density and diffusion coefficient are anomalous.…”

Single-file mobility of water-like fluid in a generalized Frenkel-Kontorova model

“…19,20 Besides these models, effective models have been widely employed in order to study anomalous behavior in bulk water-like systems. [21][22][23][24][25] In these effective models is considered that bulk water form small clusters of four water molecules, and that these clusters come together to form water bicyclo-octamers of different densities. However, in confined systems, these structures are completely different and heavily dependent of the tube geometry and water model employed.…”