how to add this into my own data base

[hxie]

I have this reaction:
xA(g）+ (1-x)B(g) --> C(Ax,B(1-x)) where x and 1-x are subscripts

for example,
Si+ Ge--> SixGe(1-x)

what I need to do is to add SixGe(1-x) into my own database so I can use it in my equilibrium.
A and B are not necessarily Si and Ge.
I have define most thermal data for this AxB(1-x) compound or alloy.

this has bothered me for a while.
any suggestion will be appreciated!