centro-symmetry parameter

[thangckt]

Dear Developers,

I wonder if you can implement the centro-sysmmetry parameter into PLUMED?

The parameter is defined as

$$ CSP = \sum_{i = 1}^{N/2} | \vec{R}i + \vec{R}{i+N/2} |^2 $$

where N is a number (choosable) of nearest neighbors. This parameter has been implemented in LAMMPS, so I also wonder if you can allow extracting its value from LAMMPS and use as MULTICOVAR in PLUMED? I see the pull request #83 from 2014, and hope that this feature is available now?

Thank you so much.

[GiovanniBussi]

Hi, #83 is done and indeed allows passing CVs from the MD code. We used it e.g. for alchemical metadynamics. However, for this to work, you need to code in the PLUMED class within LAMMPS to possibility to pass this variable.

Regarding the possibility to directly compute this in plumed, @gtribello likely knows better than me.

[thangckt]

Dear Prof. @GiovanniBussi

Thank you so much for your guide. I will ask Prof. @gtribello whether if he can help?

About your instruction

"you need to code in the PLUMED class within LAMMPS to possibility to pass this variable"

can you give a little detail on which code we need to modify in LAMMPS? or do you have any guiding docs for a case that can be applied with an existing parameter in LAMMPS? I will very much appreciate that.

Thank you so much for your help.