[QE-users] Doubt in performing vc relax and relax - Reg

[Husak Michal]

You are wrong.
During scf you do not change lattice parameters.
Relax is used when you are sure about lattice parameters - eg. from X-ray diffraction.
________________________________
From: users <users-bounces at lists.quantum-espresso.org> on behalf of singaravelan T R <trsingaravelan27 at gmail.com>
Sent: Sunday, April 18, 2021 8:38:16 AM
To: users at lists.quantum-espresso.org
Subject: [QE-users] Doubt in performing vc relax and relax - Reg

Dear all,
I think vc - relax and relax are nearly the same things by following arguments. If wrong please correct me.

In case of relax calculation, we check for atomic position optimization, and then separately do the lattice parameter vs total energy by running scf, Optimization.

But in case of vc - relax we do both (lattice parameter and atomic position optimization) in a single go. I think that vc- relax is more suitable if we need to optimise a, c and also atomic position by running scf.

And relax is suitable if we need to optimize  a and atomic position alone. All these things are in context of bulk systems like silicon.
with thanks,
Singaravelan T R