[CP2K-user] What is the principle of &fixed_atoms?

[Daeyun Lee]

Dear Matt

First of all, I'm sorry.
Now I noticed that coordination is wrong.
I mean "coordinates".



Do you mean &fixed_atoms and cell parameters are independent?

Well, in my case, xyz lengths of the cell and the distances among atoms are 
the same, because all fixed atoms form the cell frame(a cube shape).
I have already checked and confirmed that they are the same length.

The coordinates should have been fixed with &fixed_atoms, according to 
manual.
Nevertheless coordinates of atoms were changed at the output.

I don't understand this.


2020년 8월 6일 목요일 오후 6시 51분 6초 UTC+9, Matt W 님의 말:
>
> To my knowledge it fixes the cartesian position of the atoms listed. The 
> cell parameters are free to adjust if you perform a cell optimization.
>
> Matt
>
> On Wednesday, August 5, 2020 at 11:49:06 AM UTC+1 ka... at gmail.com 
> wrote:
>
>> Hello, everyone
>>
>>
>> I try to optimize cell coordinate with &fixed_atoms.
>> I thought that it will be optimized not to change coordination because of 
>> the word "fix"
>> and I read the manual says that "specifies a list of atoms to freeze".
>>
>> But I noticed that the coordination is changed somewhat at the output 
>> file.
>> What is the principle of the &fixed_atoms?
>> Doesn't it just freeze or fix the coordination?
>>
>> This is a part of my input.
>> &MOTION
>>   &CELL_OPT
>>     KEEP_ANGLES .T.
>>   &END CELL_OPT
>>    &CONSTRAINT
>>      &FIXED_ATOMS
>>         LIST 1..56
>>      &END FIXED_ATOMS
>>    &END CONSTRAINT
>> ...(omission)...
>>
>>   &SUBSYS
>>     &CELL
>>       ABC              10.166 10.166 10.166
>>       ALPHA_BETA_GAMMA 90.0   90.0   90.0
>>       PERIODIC  XYZ
>>       MULTIPLE_UNIT_CELL  1 1 1
>>     &END CELL
>> ...(omission)...
>>
>> And, at the output file, the cell vector ABC was changed to 10.436 at the 
>> Fe2+ lattice, to 10.447 at the Zn2+ lattice and so on.
>>
>> If anyone understands about this, please tell me.
>>
>>
>> Thanks for your attention.
>>
>
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