State diagrams boundary location

The equilibrium phase boundaries between solid and liquid, solid and gas, and liquid and gas for a single component are represented by a line on a pressure-temperature diagram as shown in Fig. 12.1. The state of coexistence of all three phases in equilibrium is represented by the triple point [1]. In Fig. 12.2, one can see a snrface in the three-dimension space of state variables [pressure (P), mass density (p) and temperature (7)] and the projections of the state surface on the planes (P, T) and (P, 1/p). The three usual states of matter are separated by Coexistence Curves. If the values of (P, T) are such that the component s state is located inside a coexistence curve, then the pure component is observed under the form of two coexisting phases. 

Figure 3.1.9 shows the general location of the phase boundaries between the solid, the liquid, and the gas phase and the respective diagram for water. Note the small decrease of the melting temperature with increasing pressure, which is the result of the anomaly of water by which the liquid phase has a higher density than ice. All three phases are in equilibrium at the triple point. If the temperature and pressure exceed the so-called critical values, 374 °C and 218bar for water, the phase boundary between liquid and vapor vanishes. For this supercritical state, a... 

Fig. 21. Phase diagram for superconducting UPtj with external field H along c. Open and solid circles are ftorn a.c. susceptibility data, while triangles are locations of torsional oscillator anomalies (Kleiman et al. 1989). The shaded area represents the boundary between states where antiferromagnetic intensity varies with field and temperature and where it is H and T independent. The dashed lines are trajectories followed to accumulate dilTraction data. (From Aeppli et al. 1989.)...

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