[CP2K-user] [CP2K:19014] Re: TiO2 slab not converging

Léon Luntadila Lufungula Leon.luntadilalufungula at uantwerpen.be
Wed Jun 28 12:15:57 UTC 2023

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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