[QE-users] Adsorption studies

[Paolo Costa]

Dear Hande,

thanks for your detailed information and sorry for the late reply.
Actually I found out the mistake. When I performed optimization of the slab
surface alone I kept fix some atoms position.

By the way, I thought to implement van der Waals corrections (!vdw_corr
='grimme-d3'). Can I use such correction with any pseudopotentials?

Thanks again

Paolo

2018-07-26 10:30 GMT-04:00 Hande Toffoli <ustunel at metu.edu.tr>:

> Dear Paolo,
>
> Assuming everything was set up correctly (for which I would have to see
> your input files), the magnitude of the adsorption energy is way too large
> to be accounted for by dipole corrections. What I would suggest is for you
> to isolate the TiO2 slab from Anastase_Surface_without_H_anisole_1.out
> and run an scf calculation on it. I would then see what the difference is
> with the final energy you obtain from Anastase_Surface_without_H.out. If
> the difference is very large, there's your answer. This suggestion is
> triggered by the observation that the reconstruction on the "bottom"
> surface of the slabs in the two output files appears different. This may
> not be the answer but worth a shot.
>
> Beyond this, there are a couple things to note about your calculations.
> The first one is that it appears that you are not using van der Waals
> corrections. Since your molecules are perpendicular, it shouldn't matter
> that much but most commonly, such a molecule would adsorb in the parallel
> configuration, so presumably you will investigate that configuration as
> well. So it may be worthwhile investigating the effect of some vdW schemes.
> Secondly, your molecule appears to travel a lot on the slab during the
> geometry optimization. This is a little unusual, I would investigate this.
>
> Hope this helps.
> Hande
>
> On Wed, Jul 25, 2018 at 7:01 PM, Paolo Costa <paolo.costa85 at gmail.com>
> wrote:
>
>>
>> Dear experts,
>>
>> I got nonsense value of adsorption energy by computing 4-iodoanisole on
>> top of TiO2 anastase surface (101).
>> By calculating : (Esurface+anisole)-Eanisole-Esurface, I got an
>> adsoprtion energy of 0.66 ry (8.98 eV), which is too high.
>> Now I am trying to apply the dipole correction to see if this is the
>> problem causing an unusual adsorption energy.
>> In attachment I put the output files.
>> I would be glad to receive any suggestions to understand the problem.
>>
>> Thanks.
>>
>> Paolo
>> --
>> Paolo Costa, Ph.D.
>> Postdoctoral Researcher
>> Department of Chemistry and Biomolecular Sciences
>> University of Ottawa
>> 10 Marie Curie, Ottawa, ON K1N 6N5, Canada
>> Room number: DRO 326 (D'Iorio Hall)
>>
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>
>
>
> --
> Hande Toffoli
> Department of Physics
> Office 439
> Middle East Technical University
> Ankara 06800, Turkey
> Tel : +90 312 210 3264
> https://www.compmatsci.com/
>
>
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>



-- 
Paolo Costa, Ph.D.
Postdoctoral Researcher
Department of Chemistry and Biomolecular Sciences
University of Ottawa
10 Marie Curie, Ottawa, ON K1N 6N5, Canada
Room number: DRO 326 (D'Iorio Hall)
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