Relation between occupation in the first coordination shells and Widom line in core-softened potentials

Abstract

Three core-softened families of potentials are checked for the presence of density and diffusion anomalies. These potentials exhibit a repulsive core with a softening region and at larger distances an attractive well. We found that the region in the pressure-temperature phase diagram in which the anomalies are present increases if the slope between the core-softened scale and the attractive part of the potential decreases. The anomalous region also increases if the range of the coresoftened or of the attractive part of the potential decreases. We also show that the presence of the density anomaly is consistent with the non monotonic changes of the radial distribution function at each one of the two scales when temperature and density are varied. Then, using this anomalous behavior of the structure we show that the pressures and the temperatures in which the radial distribution functions of the two length scales are equal are identified with the Widom line.

Core-softened water–alcohol mixtures: the solute-size effects

“…In fact, for ethanol the TMD line vanishes at χ alc = 0.10, while for 1-propanol the TMD is only observed at χ alc = 0.01the TMD lines are shown in the figure 4(a). The water anomalous behavior is related to the competition between two liquids that coexist [14,88,89]. This competition can be observed using the g ww (r).…”

Two structural relaxations in protein hydration water and their dynamic crossovers

“…[39][40][41][42][43][44]. The FSC of the structural α-relaxation in water has been related to the crossing of a liquid-liquid Widom line [45][46][47][48][49][50][51][52][53] (WL), the line of collapse of the maxima in response functions that converge to a liquid-liquid critical point (LLCP). 39,40,54 Therefore the FSC that we found could be the trace of the presence of a WL and consequently of a LLCP in the phase diagram of protein hydration water.…”

The Widom line and dynamical crossover in supercritical water: Popular water models versus experiments

“…Widom line associated with the presence of a possible liquidliquid critical point. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] In the region of the gas-liquid transition, it is generally observed that departing from the critical point and entering into the supercritical region the maxima of the response functions progressively weaken. The range of definition of the Widom line is particularly relevant for water since it is equivalent to the range where the peculiar properties of supercritical water are evidenced.…”