We show that a system of particles interacting through the exp-6 pair potential, commonly used to describe effective interatomic forces under high compression, exhibits anomalous melting features such as reentrant melting and a rich solid polymorphism, including a stable BC8 crystal. We relate this behavior to the crossover, with increasing pressure, between two different regimes of local order that are associated with the two repulsive length scales of the potential. Our results provide a unifying picture for the high-pressure melting anomalies observed in many elements and point out that, under extreme conditions, atomic systems may reveal surprising similarities with soft matter.
The anomalous behavior of a two-dimensional system of Hertzian spheres with exponent $α= 7/2 $ has been studied using the method of molecular dynamics. The phase diagram of this system is the melting line of a triangular crystal with several maxima and minima. Water-like density and diffusion anomalies have been found in the reentrant melting regions. Noteworthy, a density anomaly has been observed not only in the liquid and hexatic but also solid phase. The calculations of the phonon spectra of longitudinal and transverse modes have yielded negative dependence of the frequency of transverse m…
2D competitive systems shows a large variety of solid and aggregate patterns, re-entrant fluid phase, a continuous melting as predicted by the KTHNY theory and, in some cases, waterlike anomalies. In this paper, we employ Langevin Dynamics simulations of a ramp-like core-softened fluid that have two characteristic length scales and all the features mentioned above. Analyzing the fluid phase of this system, Bordin and Barbosa [Phys. Rev. E 97, 022604 (2018)] reported the existence of two waterlike anomalous region. Now, we revisit this problem focusing in the low temperature regime and a larger…
We present a comparative computer simulation study of the phase diagrams and anomalous behavior of two-dimensional ($2D$) and quasi-two-dimensional ($q2D$) classical particles interacting with each other through isotropic core-softened potential which is used for a qualitative description of the anomalous behavior of water and some other liquids. We have shown that at the low density part of the phase diagram an increase in the width of the confining slit pore leads to a considerable decrease in the melting temperature while at high densities the melting temperature is almost unchanged.
Despite water is the most studied substance in the Earth, it is not completely understood why its structural and dynamical properties give rise to some anomalous behaviors. Interesting properties emerge when experiments at low temperatures and/or high pressures, are performed. Here we report dielectric measurements of cold water under constrained conditions, i.e. water that below the melting point can not freeze. The inner pressure shifts the α relaxation peak to similar frequencies as seen in ice Ih. Also, when we reach the triple point at 251 K, ice III seems to form. As far as we know, this…
Long-wavelength Mermin-Wagner fluctuations prevent the existence of translational long-range order, in two-dimensional systems at finite temperature. Their dynamical signature, which is the divergence of the vibrational amplitude with the system size, also affects disordered solids and washes out the transient solid-like response generally exhibited by liquids cooled below their melting temperature. Through a combined numerical and experimental investigation, here we show that long-wavelength fluctuations are also relevant at high temperature, where the liquid dynamics does not reveal a transi…
