[CP2K-user] [CP2K:21263] Re: How to Fix Bond Lengths Using SHAKE in CP2K?

[Marcella Iannuzzi]

 Hi ...

How did you find this syntax for the input?

Such a  constraint is defined through the use of collective variables in 
the section SUBSYS.
Then the CONSTRAINT section is as follows

&MOTION

  &CONSTRAINT

    &COLLECTIVE

      COLVAR 1

      MOLECULE 1

      TARGET 1.9275

    &END COLLECTIVE


.....


The Shake and Rattle algorithm is used to enforce it. 


Regards

On Thursday, March 6, 2025 at 4:11:23 PM UTC+1 Planck wrote:

> I am trying to run a CP2K molecular dynamics simulation where specific 
> bond lengths should remain fixed. Based on the documentation, SHAKE should 
> be used, but I keep encountering errors when defining it under &CONSTRAINT 
> or &MD.
>
> Here is my attempt:
> ```
> CopyEdit
> &MOTION 
>          &CONSTRAINT 
>                 &SHAKE
>                       ATOMS 1 2
>                       TYPE BOND 
>                 &END SHAKE 
>          &END CONSTRAINT 
> &END MOTION
> ```
>
> However, CP2K returns an error:
>
> ``` unknown subsection SHAKE of section CONSTRAINT```
>
> I also tried defining SHAKE within &MD, but CP2K does not recognize that 
> either.
>
> What is the correct way to fix bond lengths using SHAKE in CP2K? If SHAKE 
> is not supported in the latest versions, what alternative approach should I 
> use?
>
> Thank you for any suggestion and help
>

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