Dear All
I am simulating some aqueous electrolytes on graphene. In my system, I have two graphenes with a distance 10nm from each other and the electrolytes are situated in between those graphenes. However, I used the pppm K-space for long-range interaction calculation. Now I would like to stop the pairwise interaction between these two graphenes during the simulation. So, in short, how can I stop the pairwise interaction between two groups while using long-range coulombic interactions for all system?
It will be very helpful if someone provides some useful suggestions.
Thanks in advance
Jeams
Dear All
I am simulating some aqueous electrolytes on graphene. In my system, I have two graphenes with a distance 10nm from each other and the electrolytes are situated in between those graphenes. However, I used the pppm K-space for long-range interaction calculation. Now I would like to stop the pairwise interaction between these two graphenes during the simulation. So, in short, how can I stop the pairwise interaction between two groups while using long-range coulombic interactions for all system?
assuming, that the atoms in the graphene sheets are not charged (i.e.
q is 0), you can set up two groups and use neigh_modify exclude. this
won't work for charged atoms, since this only excludes the real space
contributions, not the kspace part.
other than that, you could also set up fix spring in couple mode and
set the equilibrium between the two sheets so that they are forced to
remain at a (mostly) fixed distance.
axel.
Dear Axel
Thank you very much for your suggestion.
I am sorry that I forgot to mention that my graphenes are oppositely charged (± 0.3 / atom) from each other. I used the neigh_modify exclude and fix spring couple command. In both cases, I got a similar kind of result.
My command was as I want to keep the surfaces apart from each other at least 9.5nm.
fix spring slab1 spring couple slab2 100.0 NULL NULL 9.5 0.0
Thanks in advance
Jeams
Dear Axel
Thank you very much for your suggestion.
I am sorry that I forgot to mention that my graphenes are oppositely charged (+- 0.3 / atom) from each other. I used the neigh_modify exclude and fix spring couple command. In both cases, I got a similar kind of result.
My command was as I want to keep the surfaces apart from each other at least 9.5nm.
fix spring slab1 spring couple slab2 100.0 NULL NULL 9.5 0.0
Thanks in advance
thanks in advance for what? is don't see a question here, and neither
is the a meaningful description from which a question can be inferred.
on top of that, you are ignoring what i explained to you. so thanks,
but no thanks from me. if you still want advice you have to do a
*much* better job at asking for it. perhaps you have more luck with
somebody else.
Dear Axel
Sorry for the less information
As I mentioned before I would like to exclude the interaction between two charged surfaces. I have used fix spring couple command as like
fix spring slab1 spring couple slab2 100.0 NULL NULL 9.5 0.0
I want to keep the surface apart from each other at least for 9.5nm in Z direction. However, the two surfaces are not keeping apart with this command and moving to each other due to the long-range interaction.
Now, what is wrong with my command? or which command can do this?
Thank you
now, you are asking for something *different* than what your original
question was about. you really have to work harder on asking more
specific questions and provide more details and background
information.
wanting to remove (or compensate) the force between the two sheets is
different from keeping them at a fixed distance.
for keeping the two sheets at a fixed distance, there are many more options.
1) the simplest is to immobilize them. e.g. by not including them in
the time integration or several other methods discussed on this
mailing list.
2) as an alternative to fix spring, you can also use fix spring/self
3) there also is fix controller which could be used to apply a
compensating force via fix addforce to keep the sheets at or close to
a desired distance
out of these 3 options, 1) is the easiest to implement, 3) the most
complex with multiple parameters that have to be carefully adjusted
for your specific system.
also, please realize that there is not only right or wrong, but in
many cases, there are parameters to tweak so that a feature works as
desired and the errors from the feature are small. this requires to
understand and think about what a specific feature in LAMMPS is doing
and particularly consider the impact of the various settings and
parameters associated with it. you obviously have not done this so i
strongly encourage you to do it before asking for more help after just
using cut-n-paste from the manual and say "it does not work, fix it
for me".
you cannot expect people to do your thinking and writing of your
inputs for you. after all, it would then be no longer your work.
axel.