Suggestion for Journal Club 12th August

[jan-janssen]

I would like to calculate phase diagrams for interatomic potentials and even DFT. While this is a challenging topic, with a lot of questions to address, Yuri Mishin seems to be able to calculate phase diagrams for interatomic potentials:

• NiAl: https://www.sciencedirect.com/science/article/pii/S1359645403007262
• NiCr: https://iopscience.iop.org/article/10.1088/1361-651X/aae400

He is using https://vcsgc-lammps.materialsmodeling.org and others use cluster expansion, like:

• AuCu: https://iopscience.iop.org/article/10.1088/1361-648X/ab1bbc

Finally Joerg and @sudarsan-surendralal presented the calculation of phase diagrams directly from MD. I would like to compare different methods to calculate phase diagrams. I started with the NiCr potential using SQS structures and the quasi-harmonic approximation. The results are available at:

• repo: https://gitlab.com/jan-janssen/NiCr-pyiron-example
• mybinder: https://mybinder.org/v2/gl/jan-janssen%2FNiCr-pyiron-example/master?filepath=calculation.ipynb

Still I am currently struggling how to combine the individual calculations, so I though we organise a meeting to get everybody involved who is interested. @liamhuber @samwaseda @sudarsan-surendralal @pmrv @raynol-dsouza are you interested?

[pmrv]

Would be interested, will check out the binder tonight!

Back in Stuttgart we did this for Fe/Cr & Cu/Ni with more or less the same approach as Mishin, MC and thermodynamic integration. The calculations take a bit longer though that what would comfortably fit in a session. Our code to do this is not yet public, but I could probably install a version on cmti & hook it up to pyiron, assuming I have a bit of time and we don't want to do this on the very next date (i.e. next week). I'm also very interested in using vcsgc (since we have bindings already and I haven't used it yet), but setting up our code is on my list anyway.

Using vcsgc would be cool as we had it in the journal club before and this would be a good application.

EDIT: The first reference describing the method I have for this is Au/Ni

[sudarsan-surendralal]

I like the suggestion but there is a chance that the interdepartmental task force meeting on software tools could take place on that day from 2-4 PM.

[samwaseda]

I put it at least in the CM calendar to make sure that Mira doesn't complain.

[liamhuber]

Sounds cool. One thing I remember running into with this was a problem with cell shape relaxation. My memory is foggy, but I think maybe VCSGC is incompatible with non-isotropic pressures? Also as far as I recall pyiron itself has some issues with non-isotropic pressures... Anyhow, that's a surmountable issue as long as one uses a basis set of structures that's sufficiently diverse.

I don't know how much I'll be able to actively participate in the meeting due to parental duties, but I'll at least try to log on and eavesdrop ;)

[jan-janssen]

I updated the repository - unfortunately the link slightly changed: https://gitlab.com/jan-janssen/nicr-quasiharmonic/-/tree/master It is again available on mybinder If it does not load directly, please just try again - it seems mybinder is struggling with large repositories.

[jan-janssen]

Hello everybody,

I would like to calculate a concentration temperature phase diagram for an interatomic potential.

To prepare for todays meeting, I already selected a suitable potential1 and prepared a set of quasi harmonic calculations at different concentrations, with each concentration being calculated based on an SQS structure. All the data I prepared is available in the repository2 which can be accessed with mybinder, to play around with the data.

I currently struggle with constructing the phase diagram based on the free energies I extracted from the individual phonon calculations. So if you have any experience with the construction of quasi harmonic phase diagrams that would be greatly appreciated.

After constructing an initial phase diagram based on the quasi harmonic approximation, I believe this dataset would a good benchmark to compare other methods like thermodynamic integration or variance constrained semi-grand-canonical monte carlo methods3. So there are definitely enough interesting topics for multiple journal club meetings, still for now I would like to focus on the quasi harmonic approximation.

The login details for todays meeting are:

Time: Aug 12, 2020 02:00 PM Paris Join Zoom Meeting https://zoom.us/j/93109489600?pwd=ZURJZVowR1ZOdjY4cHRDbFk1SGZVdz09 Meeting ID: 931 0948 9600 Passcode: 1B9rgy

Best regards,

Jan