Slope anomaly in the vapour pressure curve of Hg
The investigation of normally-metallic fluids at reduced densities has created considerable experimental and theoretical interest. Hensel1 has presented evidence for transitions, related to electronic properties, in both the liquid and vapour phases of Hg, and predicted that these would affect the liquid–vapour transition. We present here evidence that the vapour pressure curve of Hg, p(T), has an unusual and probably unique form in that the In p against 1/T plot showed a sharp change of slope at temperature T = T′ = 1,361 K and saturated liquid density ρL = 10.7 g cm−3. The latter is about the density at which Hensel1 deduced that the electronic mean free path equalled the mean interatomic spacing, and which he took to be associated with the electronic-property related transition in the liquid phase.
A Semi‐Empirical Equation for the Vapor Pressure of Liquids as a Function of Temperature
The slight reverse curvature in the plot of logP versus 1/T (P, vapor pressure; T, absolute temperature) may be explained on the basis of the nonideal behavior of the vapor together with the change in heat of vaporization with temperature. If it is assumed that ΔH is linear with T and that the van der Waals a/V2 term is a first approximation to the deviation from the ideal, the following equation may be obtained by integration of the Clapeyron equation: logP=A+BT+C logT+DPT2. The last term is the nonideal gas correction with constant D=a/2.303R2. With constants A, B, and C determined empirically, the equation reproduces experimental vapor pressures from the triple point to the critical point with an average deviation of 0.3 percent.
A model of the insulator-metal transition. Part II quasi-chemical equilibrium theory
Abstract A simple cubic hydrogenic lattice in the extreme tight binding approximation with only one energy band has been set up as a model for an insulator in Part I of this paper. Bound states of electrons and holes are combined using the quasi-chemical equilibrium theory to construct the electron structure of the crystal. At a particular value of a characteristic parameter all bound pairs dissociate simultaneously and a metal is obtained. The transition between the insulating and metallic ranges is sharp confirming a conjecture by Mott.