[CP2K-user] [CP2K:16555] Re: cell optimization strange values of the a, b, c vectors

[Jonathan Campeggio]

Dear Marcella,
 I am very sorry to bother you again. As reported in the literature, I have
built my slab with PBC along with x and y directions and I have put vacuum
along z. The slab is small as you pointed out very correctly, but  I am
doing some tests. Then I am running a Geometry Optimization of the slab
with the last 2 layers completely fixed (XYZ), and allowing the first two
breath along the z directions. As you can see in the position file (
pd_slab-pos-1.xyz), the z constraint on the last two layers is not
respected, despite it having been given in input. It appears that the
second section &FIXED_ATOMS is not considered by the program. What is my
error?

Thank you again for your competence and kindness,
Jonathan

Il giorno lun 7 feb 2022 alle ore 11:13 Jonathan Campeggio <
jonathan.campeggio at gmail.com> ha scritto:

> Dear Marcella,
>  thank you for your kind reply. I understand your point.
> Best regards,
> Jonathan
>
> Il giorno lun 7 feb 2022 alle ore 11:03 Marcella Iannuzzi <
> marci.akira at gmail.com> ha scritto:
>
>> Dear Jonathan,
>>
>> You are simulating a bulk system, not a  (111) surface.
>> In order to expose a surface, you should add vacuum in the direction
>> orthogonal to the surface you want to expose, i.e., you should use a slab
>> model.
>> The size 3x2x1 is rather small and probably not suitable to simulate the
>> Pd(111) surface. Consider to increase the system size or use k-points.
>> Even if you do so, you can expect a relaxation of the topmost layers, but
>> not a contraction in the lateral directions.
>>
>> Regards
>> Marcella
>>
>> On Monday, February 7, 2022 at 8:59:00 AM UTC+1 jonathan.... at gmail.com
>> wrote:
>>
>>> At the attention of the CP2K community,
>>>
>>> I have done a cell optimization for a Pd 111 surface. From the
>>> experimental cif I have prepared a 111 unit cell. Then I have translated in
>>> the x y z directions of 2 3 1 respectively, using periodic boundary
>>> conditions.
>>>
>>> In the attachment you can find input, output and the coordinates. I
>>> expected that the cell would "breath" in the 3 dimensions, while along x it
>>> is contracted. Is my idea wrong? Have I done mistakes in the input files.
>>>
>>> Thank you for your competence and kindness.
>>> Jonathan
>>>
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