Dear LAMMPS Users,
I am a new person to this community of LAMMPS software. Few days before I have go through the LAMMPS manual. I have a query about using finite size spherical particle in LAMMPS simulation. In documentation the pair potentials for finite size particles are given, but I want to set the interaction between two spheres as Lennard-Jones is it possible? Because the Pair_style lj/cut is not there in this finite size pair potential section. In this case the torque will not be generated as lj/cut is not doing this, So if I want to do a simulation to account for the rotation of the sphere as well as Lennard-Jones interaction with its environment, Is it possible do that in LAMMPS…What can be the atom_styles and pair_styles for this kind of simulation in LAMMPS…
Any information and help will be a great favor for me…
Thanking You…
-Deepthi Gomez
Dear LAMMPS Users,
I am a new person to this community of LAMMPS software. Few days before I have go through the LAMMPS manual. I have a query about using finite size spherical particle in LAMMPS simulation. In documentation the pair potentials for finite size particles are given, but I want to set the interaction between two spheres as Lennard-Jones is it possible?
no, because lennard-jones interactions are between the centers of the
particles only and thus cannot create a torque (as is true for all
pairwise interactions that depend on the distance only).
axel.
First of all Thank you Sir for your response… Then I have a doubt, If I can add an external force on these spheres that will cause the rotation of these spheres and I can set the environment as some polymers. Then this Lennard-Jones interaction can be applied between the spherical particles and polymers. But then is it possible to account for rotation? As lj/cut will not update this torque as well… So if I want to do something like a rotational diffusion of a spherical particle in a polymeric environment what should I do? Is it beyond LAMMPS scope?
Thanking You…
-Deepthi Gomez
Dear LAMMPS Users,
I am a new person to this community of LAMMPS software. Few days before I have go through the LAMMPS manual. I have a query about using finite size spherical particle in LAMMPS simulation. In documentation the pair potentials for finite size particles are given, but I want to set the interaction between two spheres as Lennard-Jones is it possible?
no, because lennard-jones interactions are between the centers of the
particles only and thus cannot create a torque (as is true for all
pairwise interactions that depend on the distance only).
axel.
First of all Thank you Sir for your response.... Then I have a doubt, If I can add an external force on these spheres that will cause the rotation of these spheres and I can set the environment as some polymers. Then this Lennard-Jones interaction can be applied between the spherical particles and polymers. But then is it possible to account for rotation? As lj/cut will not update this torque as well.. So if I want to do something like a rotational diffusion of a spherical particle in a polymeric environment what should I do? Is it beyond LAMMPS scope?
you are now the fourth person (or rather fourth e-mail address) asking
this same kind of question to study the same kind of system with the
same issue of not understanding what you are doing and suggesting a
model that makes little sense in the way it is described. i am getting
tired of having to explain the same things over and over again. please
read through the e-mail archives to see previous discussions.
in short, yes you can add a custom fix to add this torque, but no,
LAMMPS doesn't have this currently implemented. there is a fix
addtorque, but that is a very different beast.
in that case you are *not* using an extended particle, but are
composing one implicitly from combining multiple point particles using
regular pairwise interactions (like lennard-jones)
if you are not able to design a suitable model yourself (and that
seems to be the case here), then you have to improve your
understanding of the underlying physics and look for something that
somebody else has done (and published!) that does what you want to do.
then all you have to do follow the description and look up in the
LAMMPS documentation how to do it, and implement the missing pieces,
if needed.
please understand that the primary purpose of this mailing list is to
help people with "technical" problems using LAMMPS, discuss
(technical) problems, bugs, new features, limitations,
installation/compilation issues, but not to teach people how to do
their research. that is the job of the respective PI, supervisor,
tutor, senior colleague or similar. this is independent of the MD code
anyway.
axel.
sorry for this question…I will look into the e-mail archive
Thank you sir…
First of all Thank you Sir for your response… Then I have a doubt, If I can add an external force on these spheres that will cause the rotation of these spheres and I can set the environment as some polymers. Then this Lennard-Jones interaction can be applied between the spherical particles and polymers. But then is it possible to account for rotation? As lj/cut will not update this torque as well… So if I want to do something like a rotational diffusion of a spherical particle in a polymeric environment what should I do? Is it beyond LAMMPS scope?
you are now the fourth person (or rather fourth e-mail address) asking
this same kind of question to study the same kind of system with the
same issue of not understanding what you are doing and suggesting a
model that makes little sense in the way it is described. i am getting
tired of having to explain the same things over and over again. please
read through the e-mail archives to see previous discussions.
in short, yes you can add a custom fix to add this torque, but no,
LAMMPS doesn’t have this currently implemented. there is a fix
addtorque, but that is a very different beast.
in that case you are not using an extended particle, but are
composing one implicitly from combining multiple point particles using
regular pairwise interactions (like lennard-jones)
if you are not able to design a suitable model yourself (and that
seems to be the case here), then you have to improve your
understanding of the underlying physics and look for something that
somebody else has done (and published!) that does what you want to do.
then all you have to do follow the description and look up in the
LAMMPS documentation how to do it, and implement the missing pieces,
if needed.
please understand that the primary purpose of this mailing list is to
help people with “technical” problems using LAMMPS, discuss
(technical) problems, bugs, new features, limitations,
installation/compilation issues, but not to teach people how to do
their research. that is the job of the respective PI, supervisor,
tutor, senior colleague or similar. this is independent of the MD code
anyway.
axel.