New Structural Anomaly Induced by Nanoconfinement

\par In this work we explore the structural properties of anomalous fluids confined in nanopores
using molecular dynamic simulations. The fluids are modeled by spherical particles
that interact through core-softened potentials given by a
repulsive shoulder and an attractive well at a further distance. The different potentials of the fluids are obtained
changing the attractive well depth. The confining nanopores are given by two fixed hydrophobic and parallel plates.
All the systems present the formation of two or three layers of particles. We studied the
translational order parameter $t$ and the excess entropy $s_2$ of the particles near to the nanopore walls (contact layer).
In normal fluids, for fixed temperatures, $t$ increases monotonically with the density and
$s_2$ decreases monotonically with the density. Meanwhile, in anomalous fluids, like in water and silica, the parameter $t$
presents a region of decreasing with density and $s_2$ presents a region of increasing with density.
Under hydrophobic confinement, we found another unusual behavior. When the attractive well of the core-softened
potential is shallow, the systems present a transition between two and three layers and
the parameters $t$ and $s_2$ present a second region of anomalous behavior. For attractive
well deep enough, the systems do not present the structural transition neither the second region of structural anomaly.
Our results indicate that the confinement induces the fluid to exhibit a new behavior, not observed in bulk
systems [1].

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[1] Leandro B. Krott, Jos? R. Bordin and Marcia C. Barbosa. {\it{New Structural Anomaly Induced by Nanoconfinement}}.
J. Phys. Chem. B, v. 119, p. 291-300, 2015.