Clapeyron matching condition

Figure 11.10 Schematic representation of co-Clapeyron vector orientations of (a) base T), P) vectors and (b) resultant Clapeyron vectors X) (dotted), illustrating the geometrical condition (11.165a) for coexistence of a (solid line) and /3 (dashed line) phases. The coordinate origin is marked with a small square in each panel. [Vector lengths, angles, ya, and ASap, AVap, values are chosen purely for illustrative purposes the Clapeyron-matching condition cannot be sensibly illustrated in Si-based units for any real system (Sidebar 11.6).]...

The Clapeyron vector (evidently closely related to the coexistence coordinate a) at saturation cf. Section 11.5) is merely the projection of the GD vector (11.141b) onto the nonsingular space spanned by T), P). In terms of this vector, the coexistence condition (11.154) can be written as the Clapeyron matching condition ... 

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