[CP2K-user] [CP2K:19018] Re: TiO2 slab not converging

[Léon Luntadila Lufungula]

I really feel like something is off, because it really does not seem to 
want to converge. For the anatase unit cell CELL_OPT it easily optimized in 
just a few steps, but there I used k-points as it was much faster than 
supercell calculations and thus had to use traditional diagonalization 
instead of OT. I'll attach the input and output file for this calculation 
if this would help in any way 

On Wednesday, 28 June 2023 at 15:46:08 UTC+2 Léon Luntadila Lufungula wrote:

> Hi Matthias,
>
>  
>
> Thanks for you reply!
>
>
> I looked at my CIF file in various visualization software and it looked 
> okay there. Is there a way to check this via CP2K to be sure?
>
> I also have some preliminary results of some ongoing calculations with 
> DIIS/FULL_ALL and DIIS/FULL_SINGLE_INVERSE and these seem to be a bit 
> faster than CG but reaching convergence is still a big issue (see 
> attachments).
>
> Best,
> Léon
>
> On Wednesday, 28 June 2023 at 15:35:32 UTC+2 Krack Matthias wrote:
>
>> Hi Léon
>>
>>  
>>
>> Did you check the set of atomic coordinates read from the cif file for 
>> close contacts possibly caused by the periodic boundary conditions?
>>
>>  
>>
>> Best
>>
>>  
>>
>> Matthias
>>
>>  
>>
>> *From: *cp... at googlegroups.com <cp... at googlegroups.com> on behalf of 
>> Léon Luntadila Lufungula <Leon.luntad... at uantwerpen.be>
>> *Date: *Wednesday, 28 June 2023 at 14:16
>> *To: *cp2k <cp... at googlegroups.com>
>> *Subject: *[CP2K:19014] Re: TiO2 slab not converging
>>
>> I forgot to add the cif file which is read with the input, so here it is 
>> if someone needs it.
>>
>> On Wednesday, 28 June 2023 at 13:54:37 UTC+2 Léon Luntadila Lufungula 
>> wrote:
>>
>> Update:
>>
>> I tried to optimize a 3-layer slab with altered SCF cycle settings (inner 
>> loop: 15 steps, outer loop: 45 steps) and still it does not converge. The 
>> convergence goes towards 2E-7 after 22 outer SCF cycles, but then doesn't 
>> seem to get lower (see attachment a101-3-layer-jobID_188.out). I tried to 
>> restart the calculation with altered EPS_SCF (= 1E-6) and then the 
>> restarted SCF cycle converges as the convergence was already below 1E-6. 
>> Unfortunately, after that the SCF again seems to only very slowly converge, 
>> after 27 outer SCF steps it's still only at 8E-5 convergence (see 
>> attachment a101-3-layer-jobID_189.out). Can anybody please help me out? I 
>> feel like the calculation is not converging properly, as after nearly 2 
>> hours it still hasn't converged one SCF cycle but I don't know what might 
>> be wrong orhow to fix it... Requiring 300+ steps to reach SCF convergence 
>> seems quite high to me and makes me start to think there is something 
>> fundamentally wrong with my input. If anyone could look at my inputs and 
>> tell me what's wrong with them, I would be forever thankful!
>>
>> Kind regards,
>>
>> Léon 
>>
>> P.S. Could the TZVP basis set pose a problem? I often see people use 
>> DZVP-SR for similar calculations, but my promotor and co-promotor both told 
>> me that TZVP is required for proper energetics and should be used in 
>> production runs.
>>
>> On Wednesday, 28 June 2023 at 10:04:07 UTC+2 Léon Luntadila Lufungula 
>> wrote:
>>
>> Dear all,
>>
>>  
>>
>> I am trying to determine the ideal slab thickness for an anatase (101) 
>> slab but my SCF cycles are not converging. I optimized the cutoffs for the 
>> anatase bulk and did a CELL_OPT calculation on the unit cell to get the 
>> converged structure. From this optimized unit cell, I then used ASE to 
>> build the (101) slabs  with a 20 Å vacuum width and thicknesses varying 
>> from 2 to 12 layers. During the GEO_OPT calculation I keep the bottom layer 
>> frozen to act as the bulk. I started the 2-layer calculation yesterday but 
>> when I looked at the output today, I see that the SCF cycle fails at every 
>> step of the geometry optimization (see output in attachment). Is there 
>> something wrong with my setup (too tight convergence criteria, wrong SCF 
>> setup, ...), or is it because a 2-layer structure is perhaps too small? The 
>> changes in energy go to 1E-5 - 1E-6 but never reach the convergence 
>> criteria of 1E-7 even after 300 steps (inner cycle: 10 steps, outer cycle 
>> 30 steps). I would guess that it could converge if I would increase the 
>> maximum number of steps, but 300 steps already seems quite a lot to me, 
>> although I could be wrong...
>>
>>  
>>
>> If anyone could share their thoughts on the situation so I can continue 
>> my work, I would greatly appreciate the help! Thanks in advance!
>>
>>  
>>
>> Best regards,
>>
>> Léon
>>
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>>
>

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