How to determine the final crystal structure after SSCHA minimisation?

[jgSi1113]

Dear SSCHA developers,

Recently, I used the SSCHA code to minimize the dynamic matrix and to study the influence of qauntum effects on the system I concerned. After SSCHA minimisation, the log says the system is under 2.8 GPa, and the structure I used is fully relaxed without any pressure. Does it mean that the structure changed when the quantum effects are taken into account? How can I output the structure after SSCHA minimisation? Or is it just an auxiliary pressure value likes the SSCHA frequency?

Best & Regards!
Jianguo Si

[mesonepigreco]

Hi,
it depends on the kind of run you made.
The structure is stored inside the final dynamical matrix, which you can inspect. You can save it in other formats:

# [here the sscha minimization code]
minim.run()

# save the structure of the final dynamical matrix in QuantumESPRESSO format
minim.dyn.structure.save_scf("my_final_structure.scf")

You can inspect the structure here. The final stress is the real value of the stress, accounting for quantum and thermal effects; see PRB, 98, 024106, 2018.

In your case, you did not change the unit cell to relax the stress. If you want to, check how to do a SSCHA vc_relax from this tutorial.

[jgSi1113]

Thanks for your kindly reply. It's more clear for me.

Regards!
Jianguo