4He glass phase: A model for liquid elements

Abstract

Abstract:The specific heat of liquid helium confined under pressure in nanoporous material and the formation, in these conditions, of a glass phase accompanied by latent heat are known. These properties are in good agreement with a recent model predicting, in liquid elements, the formation of ultrastable glass having universal thermodynamic properties. The third law of thermodynamics involves that the specific heat decreases at low temperatures and consequently the effective transition temperature of the glass increases up to the temperature where the frozen enthalpy becomes equal to the predicted value. The glass residual entropy is about 23.6% of the melting entropy. IntroductionThe solid-liquid transformation of bulk helium depends on the pressure p and temperature T [1-6]. The melting entropy is determined from the Clapeyron relation knowing the volume and melting temperature changes associated with the solid-to-liquid transformation under a pressure p [2]. The phase diagram is deeply modified when liquid helium is confined in 25Ǻ mean diameter nano-pore media under pressures p where 3.58 ≤ p≤ 5.27 MPa [7]. Early studies of these involved specific heat anomaly measurements and they were viewed as a consequence of the formation of localized Bose-Einstein condensates on nanometer length scales analogous to a solid [7]. The glass phase has since been discovered using measurements of the static structure factor, S(Q), of helium confined in the porous medium MCM-41 with pore diameter 47±1.5 Å. A similar amorphous S(Q) was also observed in 34 Å Gelsil [8]. The presence of an amorphous phase has been confirmed at higher pressures using porous Vycor glass [9]. In this work we consider that the supercooled liquid far below the melting temperature T m is condensed in a glass phase accompanied by an exothermic latent heat associated with a first-order transition.

Prediction of Second Melting Temperatures Already Observed in Pure Elements by Molecular Dynamics Simulations

“…The main conclusions of this chapter are the first-order character of the transition from liquids state to the glassy state and the second-order phase transition from the glassy state to the ordered Liquid 3 along Line 4 in Figure 3 . This point was not raised in previous publications considering that the first-order character was reversible [ 72 , 75 , 76 ].…”

“…The enthalpy coefficients ∆ε lg0 of Phase 3 being equal to zero at T m , the glass transition occurs at T g during cooling through a first-order transition and an exothermic latent heat equal to ∆ε lg (θ g ) [ 72 ]. Liquid 4 He in a confined space under pressure is amorphous and undergoes a transition during heating which looks like a first-order transition [ 73 , 74 , 75 ].…”

Homogeneous nucleation of phase transformations in supercooled water

“…This model also explains the presence of intrinsic nuclei above Tm submitted to the Laplace pressure of liquid [47,48], predicts the latent heat of the first-order transition from liquid helium under pressure to a glass phase [49] and the Lindemann constant of pure liquid elements [50].…”

Residual Entropy and Critical Behavior of Two Interacting Boson Species in a Double Well

“…This entropy is defined as the Equilibrium Entropy . However, several physical systems ranging from, e.g., water ice [ 23 , 24 ], carbon monoxide [ 25 ], highly pressurized liquid-helium [ 26 ], glass systems [ 27 , 28 ], proteins [ 29 ], and even black-holes [ 30 , 31 ], seem to manifest a residual content of information (corresponding to a residual entropy) for . The presence of such residual entropy has been generally associated with residual degrees of freedom at such as, among others, ground-state degeneracy, residual structural disorder, geometrical frustration and entanglement.…”