Phonons and asr

[litman90]

It would be useful/necessary to write the phonon branch in such a way that it can be called from another type of calculation when it is necessary to compute a hessian.
It also has to contemplate the necessity of having checkpoint files during hessian calculation.

I don't see how could be implemented in a clean and general way.

Regarding asr and moment of inertia calculation, are you ok if I move these things to a new file in utils folder so they can be called from other parts of the code?

[mahrossi]

Ok. Regarding the first point we need to discuss "deeply". @ceriottm we thought it would be good to do it when we are all in Lausanne.

Regarding the checkpoint file, what do you mean? The partial Hessian and dynamical matrices are written at intermediate steps (at least they were last time I checked). So it is already possible to restart. Do you mean something else?

ASR and related should definitely go to some sort of "tools" routine, you are right. If you want to do that in a clean way that doesn't break anything in the code, my vote is for you to go ahead,