Plotting Phase Diagrams (Temperature vs Composition)

AI Thread Summary
The discussion focuses on plotting phase diagrams for a binary metal system using the Clapeyron equation, specifically the formula ln(x) = ΔH/(R)(1/TA - 1/T). The user is attempting to plot temperature versus composition for a eutectic system with a eutectic temperature of 850°C and an enthalpy of fusion of 2500 cal/mol. However, the resulting graph in Matlab does not resemble a typical eutectic graph, with the eutectic point appearing significantly lower than expected. Concerns are raised about the reliability of the Clapeyron equation due to its assumptions, particularly regarding the purity of the solid state. The user seeks alternative equations or methods to accurately plot the binary eutectic phase diagram.
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I'm planning to plot phase diagrams of Temperature vs Composition. I found the formula ln(x) = \frac{\Delta H}{R} (\frac{1}{T_A} - \frac{1}{T}) from the Clapeyron equation.

Its a ideal solution of 2 metals in L state and regular solution in S state. Eutectic temperature is at 850C and enthalpy of fusion is \Delta H = 2500 cal/mol (which I converted to 10460 joules) with heat capacity constant, and both materials melt at T_A = 1000C. Rearranging to make T the subject got me T = \frac{1}{\frac{1}{T_A} - \frac{R ln(X_A)}{\delta H}

T = \frac{1}{\frac{1}{T_A} - \frac{R ln(X_A)}{\delta H}

However the graph that I get when plotted out in Matlab does not look like a eutectic graph. I plotted 1-X and X for both metals, and T=1150 for the eutectic line but they don't seem to match. The eutectic point is way lower than the eutecetic line. Did I do something wrong? Thanks!

http://img340.imageshack.us/img340/5455/54676710.jpg
 
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The Clapeyron equation relies on some simplifying assumptions, one of which is that the solid state is absolutely pure. I wouldn't expect it to be perfectly reliable far away from x_B=0 or 1.
 
Is there a better equation to use to plot out the binary eutectic phase diagram?
 
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