FEATURE: Quasi-harmonic Approximation

[JaGeo]

Describe the feature

Build a quasi-harmonic workflow on top of the EOS Maker.

• [ ] Reuse equation of state maker
• [ ] Adapt the optimizations to constant volume runs with flexible lattice parameters
• [ ] Start a (harmonic) phonon run for each optimized structure
• [ ] check if band structures are free of imaginary modes
• [ ] compute thermodynamic properties based on qha for structures without imaginary modes
• [ ] compute thermal Expansion curves

This would be incredible useful. I plan to draft an implementation with the forcefields as we need this for a current project

[JaGeo]

@esoteric-ephemera I will try to add an additional output for all optimized to the EOS state output. Do you see any potential issues I might overlook for the EOS maker? Otherwise, I will simply make it an optional step.

[esoteric-ephemera]

Hi @JaGeo: I don't see any pitfalls to using use the EOS workflow in a QHA phonon workflow. Let me know if anything there isn't working as intended, I'm happy to contribute directly if that would help!

[JaGeo]

@esoteric-ephemera I have started with a draft. I will finish this in the next months - at least with basic functionality - as we require this implementation for a project.