Plotting Phase Diagrams (Temperature vs Composition)

[nyxynyx]

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

 

[Mapes]

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.

 

[nyxynyx]

Is there a better equation to use to plot out the binary eutectic phase diagram?

 

[nyxynyx]

Im still unable to figure this out... need a little help thanks :)