[QE-users] cell_dofree with BFGS relaxation

[Lorenzo Paulatto]

there are several quircks:

I see you did not specify ion_dynamics="damp" when doing damped 
dynamics, I'm not sure what happens of the ions in this case.

The "BFGS" output you sent me is contains 14 steps of BFGS optimization, 
followed by one step of (damped?) molecular dynamics

The damped dynamics run stops because it reaches the maximum of 50 
iterations (nstep=50) not because it has converged, but the cell it 
obtains is pretty much identical to the BFGS one

hth

On 30/04/2019 13:55, Daniel Marchand wrote:
> Thanks, Lorenzo, for the rapid response. I have a bit of a concern w.r.t 
> the z-only relaxation. When I use BFGS the z component of all the axis 
> are allowed to relax. However, I do not want this, I want only the z 
> component of axis 3 (v3_z) to be moved, as per the description in the 
> documentation. This only seems possible with the damp algorithm. Here I 
> have attached sample input for both the bfgs and damp_pr algorithms 
> https://drive.google.com/file/d/17Bt8HHL55yG75cba6awvl8E_wo20KDYI/view?usp=sharing. 
> Perhaps I have one of the settings wrong?
> 
> Best,
> 
> Daniel
> 
> 
> On Tue, Apr 30, 2019 at 1:07 PM Lorenzo Paulatto <paulatz at gmail.com 
> <mailto:paulatz at gmail.com>> wrote:
> 
>      > 1) Is this still the case? When I enable this setting in my own
>      > calculations (QE v6.3) I see the cell does indeed allow only
>      > z-relaxation in the cell, but it does so for all the lattice
>     directions
>      > rather than just the a_3 lattice direction.
> 
>     In general cell_dofree works with BFGS, but it is true that some times
>     damped dynamics is more reliable.
> 
>     I.e. I recently did some relaxations with cell_dofree="shape", as BFGS
>     was not findign the minimum for some volumes, I just put
>         cell_dynamics="damp-pr"
>         ion_dynamics = 'damp'
>     with everything default.
> 
>     cheers
> 
>     -- 
>     Lorenzo Paulatto - Paris
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-- 
Lorenzo Paulatto - Paris