I think I found a possible solution, I put a little patch in the gitlab
tracker, I'm not sure if you get notifications.
cheers
On 4/30/19 2:49 PM, Daniel Marchand wrote:
Thanks again. So for the BFGS output, for whatever reason there is a
final SCF step, I"m not sure why. And yes, correct, the
damped_dyanmics(n=50) ~= "BFGS"(n=14).
However my concern is that for the "BFGS" the z component of all axis
changes, which for my use-case is very bad. However, for damp only the z
component of axis 3 (v3_z) is allowed to relax. Unfortunately, in my use
case (the one in the attached example) the damp method seems to converge
much much slower than BFGS. E.g. for the metrics that would affect my needs:
grep -A3 CELL_PARAMETERS pw.out.bfgs <fast convergence in cell shape,
but we see shifts in the z-component of axis 1 & axis 2, which for my
needs is very bad>
grep -A3 CELL_PARAMETERS pw.out.damp_pr <slow convergence in cell shape,
but we see that the z-component of axis 1 & axis 2 are held fixed, which
for my needs is very good>
Is there any way to make bfgs hold the z-component of axis 1 & 2 fixed,
like how we see for the damp_pr example?
Best,
Daniel
On Tue, Apr 30, 2019 at 2:16 PM Lorenzo Paulatto <[email protected]
<mailto:[email protected]>> wrote:
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
<[email protected] <mailto:[email protected]>
> <mailto:[email protected] <mailto:[email protected]>>> 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
_______________________________________________
Quantum Espresso is supported by MaX
(www.max-centre.eu/quantum-espresso
<http://www.max-centre.eu/quantum-espresso>)
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_______________________________________________
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