Distorted optimized structure (FeOOH) while GEO_OPT.

[ganta.pra... at gmail.com]

Dear Matt W,

It is complete structure, I did not cut bulk to generate my surface. My 
initial point is the optimized bulk structure. 

I have also built structure from the FeOOH unit cell and I have done slab 
simulation. The same distortion is happening. 

I dont think that this is due to symmetry or polarity (I am not 100% sure 
:) ). I am new to CP2K and QM and if you suggest some literature on how to 
check the stability of the structure before proceeding with simulations, 
that will be great for me. 

Thank you for the reply. If you have any other suggestions, do let me know.

Regards,
Prasanth. 

On Monday, July 17, 2017 at 6:59:35 PM UTC+2, Matt W wrote:
>
> Hi,
>
> have you just cut a bulk slab to generate your surface?
>
> Please check the literature - do you expect this to be a stable structure. 
> It looks like the optimization is trying to do sensible things, but the 
> start point is highly unstable (polar?). 
>
> Matt
>
> On Monday, July 17, 2017 at 5:20:23 PM UTC+1, ganta.... at gmail.com 
> wrote:
>>
>> I am doing geometry optimization of a slab (FeOOH), with 30 Angstroms 
>> vacuum in Z direction. I have done bulk optimization successfully and I am 
>> using optimized bulk structure to do slab optimization (with 30 Angstroms 
>> vacuum). The slab is not optimizing and it is heavily distorted towards 
>> vacuum region. Please let me know any ideas to avoid this distortion. 
>>
>> I am planning to use more layers (to see if that avoids distortion), but 
>> increasing more layers increases more atoms and it is computationally 
>> expensive. 
>>
>> The distortion can be seen in the attached surf001-pos-1.xyz file. I 
>> tried to see old posts about this and the structures used were 
>> comparatively small (my model 382 atoms).
>>
>> Please let me know if you have any suggestions.
>>
>> Thanks and Regards,
>> Prasanth.
>>
>>
>>
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