# [lammps-users] Spinodal Decomposition

Dear all,

Is there any way to simulate spinodal decomposition mechanism during phase seperation in dealloying process in LAMMPS? If not, does anybody know any other methods or softwares that is applicable for these kind of simulations? I need it for simulating nanofoams which are produced by dealloying processes.

Niaz Abdolrahim

You can use deform command for that.

Z.I.

Dear Z insepov,

Thank you for your reply. But could you please explain briefly by what exactly can we do with deform command with regards to phase seperation?

Thank you so much,
Niaz

By expanding the volume let say by 25% , you can easily put the system below the spinodal curve and after some delay the system goes into spinodal decomposition.

Z.I.

Dear Z Insepov,

Thanks for your explanation. But since I am very amateur in these kind of simulations (I mean spinodal decomposition), I am not very certain if my method is correct or not. Should I make a two phase volume at first (say Au-Ag alloy) or I can do it just by creating one phase volume (just Au atoms) with some voids inside? Secondly, should I apply the expansion very fast and then let the whole expanded structure to relax for some time or I should do it slowly? And my last question is what would be the proper temperature ?

Regards,

Niaz

I was talking about spinodal decomposition in a mixture or two or
three elements. There are two ways how to do that. One way it get the
bubbles of one element by letting the pressure into a very high
negative state. It automatically puts the system deep into the
unstable region. We call it "kinetic way".
You should first understand where in the P-c-T (c - concentration of
one element) plane you would like to put your system? If this needs a
negative pressure, here you can simulate the process by MD. The larger
supersaturation is, the faster the process goes.
There is another way, which we call "thermodynamic way" where you can
create the bubble and calculate the free energy of the bubble and then
to build the study of the surface tension, critical radius, etc.

Z.I.

I was talking about spinodal decomposition in a mixture or two or
three elements. There are two ways how to do that. One way it get the
bubbles of one element by letting the pressure into a very high
negative state. It automatically puts the system deep into the
unstable region. We call it “kinetic way”.
You should first understand where in the P-c-T (c - concentration of
one element) plane you would like to put your system? If this needs a
negative pressure, here you can simulate the process by MD. The larger
supersaturation is, the faster the process goes.
There is another way, which we call “thermodynamic way” where you can
create the bubble and calculate the free energy of the bubble and then
to build the study of the surface tension, critical radius, etc.

Z.Insepov
(the previous e-mail was sent by my student - please use this address)

Dr. Insepov,

What I got through your email is to simulate the whole volume of 2 element mixture and expand it by 25% as you suggested and let the system relax. Finally we should have a volume with completely separated phases. Therefore since we are interested in creating a single material foamshape structure, we can remove the phase which is supposed to dissolve during the dealloying process and let the whole system relax again for some time. Is that true? Will this process bring us to a desirable point of stable foam shape structure with ligaments of an average same size?

Thank you,

Niaz

Would you please send me some more documentation (published papers would be fine) that I will be able to understand what your system is alike? I maybe will be able to respond in more detail.

Z.I.

niaz abdorrahim wrote:

Yes for sure. These are some papers that contain the nanofoam structures which I am looking for.

Thank you for your kind attention,
Niaz