[gpaw-users] Full optimization in plane wave mode

[Marcin Dulak]

On 11/07/12 15:03, Janne Hirvi wrote:
>
> Hi,
>
> I believe that full optimization with UnitCellFilter has been 
> implemented only for plane wave mode (not for finite difference mode)?
>
> However, I will try to increase the cut-off energy (which basically 
> corresponds to decrease in grid spacing for finite difference mode)
>
> and check what happens, even though these energy changes seems to be 
> quite large.
>
i would first verify the calculations with the latest ASE/GPAW.
I heard rumors that at some point (just before Jens Jørgens leave)
there were problems with stresses. You could maybe also limit the 
optimization to stress only
with StrainFilter. If the problem persists attach the full script.

Best regards,

Marcin

> Regards,
>
> Janne
>
> *From:*Vladislav Ivanistsev [mailto:olunet at gmail.com]
> *Sent:* Wednesday, November 07, 2012 3:45 PM
> *To:* Jón Steinar Garðarsson Mýrdal
> *Cc:* Janne Hirvi; gpaw-users at listserv.fysik.dtu.dk
> *Subject:* Re: [gpaw-users] Full optimization in plane wave mode
>
> I've also experienced similar problem with grid spacing. What is the 
> lowest h value one can safely use. Is h=12 suitable?
> Ph.D. Vladislav Ivanistsev
>
> On Wed, Nov 7, 2012 at 1:33 PM, Jón Steinar Garðarsson Mýrdal 
> <jsmy at dtu.dk <mailto:jsmy at dtu.dk>> wrote:
>
> Hi Janne
>
> When you change the shape or size of your super cell then the grid 
> sampling will change and this can lead to a change in energy.
> Therefore it is important to run calculations where you perform cell 
> optimization with extra small grid spacing.
> I would try lowering the value of h you are using.
>
> Mvh.
> Jón Steinar Garðarsson Mýrdal
> Ph.d Student
> DTU Energy Conversion
> -------------------------------------------
> Technical University of Denmark
> Department of Energy Conversion and Storage
> Frederiksborgvej 399
> Building 775
> 4000 Roskilde
> Direct +45 46775818
> jsmy at dtu.dk <mailto:jsmy at dtu.dk>
> http://www.dtu.dk
>
> ________________________________________
> From: gpaw-users-bounces at listserv.fysik.dtu.dk 
> <mailto:gpaw-users-bounces at listserv.fysik.dtu.dk> 
> [gpaw-users-bounces at listserv.fysik.dtu.dk 
> <mailto:gpaw-users-bounces at listserv.fysik.dtu.dk>] On Behalf Of Janne 
> Hirvi [janne.hirvi at uef.fi <mailto:janne.hirvi at uef.fi>]
> Sent: Wednesday, November 07, 2012 2:01 PM
> To: gpaw-users at listserv.fysik.dtu.dk 
> <mailto:gpaw-users at listserv.fysik.dtu.dk>
> Subject: [gpaw-users] Full optimization in plane wave mode
>
>
> Dear GPAW-users,
>
> I tried to perform "full" optimization (in orthogonal cell) for silica 
> structure using plane wave mode.
>
> The script was something like this
>
> -----
> mixerown=Mixer(beta=0.1, nmaxold=5, weight=50.0)
> calc=GPAW(mode=PW(400), xc='PBE', kpts=(4,4,4), mixer=mixerown, 
> txt=name+'.txt')
> Bulk.set_calculator(calc)
>
> ucf=UnitCellFilter(Bulk,mask=[1,1,1,0,0,0])
> relax=BFGS(ucf)
> traj=PickleTrajectory(name+'.traj','w',Bulk)
> relax.attach(traj)
> relax.run(fmax=0.03)
> ----
>
> The corresponding calculation converged (stress and forces are small), 
> but the energies for each step
>
> Zero Kelvin:   -188.134359 (Step 1)
> Zero Kelvin:   -187.264322
> Zero Kelvin:   -187.394858
> Zero Kelvin:   -187.853520
> Zero Kelvin:   -187.879200
> Zero Kelvin:   -188.081472
> Zero Kelvin:   -188.048312
> Zero Kelvin:   -188.051650
> Zero Kelvin:   -188.081487
> Zero Kelvin:   -188.096408 (Step 10)
> Zero Kelvin:   -188.091418
> Zero Kelvin:   -188.113318
> Zero Kelvin:   -188.122375
> Zero Kelvin:   -188.072067
> Zero Kelvin:   -188.123096
> Zero Kelvin:   -188.125491
> Zero Kelvin:   -188.097103
> Zero Kelvin:   -188.125748
> Zero Kelvin:   -188.125478
> Zero Kelvin:   -188.130157 (Step 20)
> Zero Kelvin:   -188.146106
> Zero Kelvin:   -188.122699
> Zero Kelvin:   -188.065573
> Zero Kelvin:   -188.071948
> Zero Kelvin:   -188.033935
> Zero Kelvin:   -187.960727
> Zero Kelvin:   -187.975459
> Zero Kelvin:   -187.954870
> Zero Kelvin:   -187.941968
> Zero Kelvin:   -187.914349 (Step 30)
> Zero Kelvin:   -187.912083
> Zero Kelvin:   -187.911463
> Zero Kelvin:   -187.909650 (Step 33)
>
> behave quite strangely. The energy minimum has been reached around 20 
> steps (only slightly smaller than that
> for the initial guess) and the final energy is quite notably higher.
>
> Do you know if this is related to large changes in cell dimensions 
> when using plane wave mode or what might
> be the reason for this?
>
> Best regards,
>
> Janne Hirvi
>
> -----
> Janne Hirvi
> PhD (Physical Chemistry), Researcher
> University of Eastern Finland, Department of Chemistry
> P.O.Box 111, 80101 Joensuu, FINLAND
> Tel: +358 50 4422594 & +358 50 3474223
>
>
>
>
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