Hi everyone. I am a beginner in ATAT. Recently we are calculating phase diagram for CuPd binary alloy, involving BCC and FCC lattice. I use phb code in ATAT. However, for some ground states, I got the wrong phase boundary which should not happen in real world. Therefore, I try to trace phase boundary from higher temperature to lower temperature. But the problem is, how to estimate the chemical potential at finite temperature? Do I have to run emc2 at first? Then phb?
Another question is, what is the energy of disordered phase? I know we can specify -gs=-1 to represent disordered phase. But how does ATAT know its energy as it does not show up in my convex hull.
You can use emc2 first. You specify the chemical potential (mu) and the code returns the corresponding composition. If you span a range of mu you can find the mu vs x relationship (or vice-versa).
Of course, you may need to do two emc2 runs (one for each phase) and look for equality yourself. You can also get an approximation in this way: emc2 will often experience a phase transformation, so you would pick the mu when that happens. Of course, there may be hysteresis, so it’s better to approach the phase transfo from 2 directions and average to two mu where the phase transfo occur.
(you ask many questions - I will get to the other ones later)