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Re: [lammps-users] Modifying LAMMPS / accessing variable from another fix
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Re: [lammps-users] Modifying LAMMPS / accessing variable from another fix

From: Axel Kohlmeyer <akohlmey@...24...>
Date: Tue, 11 Jul 2017 06:35:24 -0400

On Tue, Jul 11, 2017 at 4:36 AM, ONOFRIO, Nicolas [AP] <nicolas.onofrio@...6977...> wrote:
Dear LAMMPS users,

We recently introduced EChemDID to equilibrate voltage during reactive MD (by adjusting the electronegativity used for charge equilibration).
The method is detailed in the JCP
I am working on updating our code to make it more consistent with latest LAMMPS versions and also trying to keep LAMMPS's code untouched.

I noticed a new variable (chizj) in the recent version of QEq which is set to zero by default and, added to the electronegativity (chi) then used to optimize charges.
I don't know why this (chizj) variable has been introduced but it looks to me as a variable to include an external potential to the QEq?

​according to the source code management system, the chizj pointer has been included in the QEQ package based class since its inception in ​september 2014.
also, it is set and used in fix qeq/slater. it is not at all present in fix qeq/reax of the USER-REAXC package.

I have a fix_echemdid that equilibrates the voltage and I was thinking using chizj to pass the external potential to the QEq.
This would allow echemdid to work directly with QEq regardless of the potential (as long as there is a potential consistent with QEq).
However, I have hard time to access the chizj variable from my fix_echemdid class.

I would like to know
- if I am proceeding the right way. Does it make sense to use chizj to pass an external potential?

- if yes, what is the best way to access chizj from my echemdid class?

​the common way in LAMMPS to expose internal data to other classes without having to know its particular type ​is through adding an "extract()" method to the class holding the data and adding the corresponding code to it.


Thank you,


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Dr. Axel Kohlmeyer  akohlmey@...12...24...
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.