Hello everyone,
I am trying to simulate collection of nanoparticles in a periodic box using
Soft sphere modelling and as nanoparticles have some amount of cohesive
force acting between them, I want to use cohesive VanderWall force between
them.
I am done with Simulation without any cohesive force (using pair_style gran
hooke). But I was searching on how to use Vanderwall force with this model,
I didnt find any potential having this Vanderwall part(only).
pair_style hybrid will be useful but what other potential should I use
alongwith pair_style gran/hooke .
Any kind of help is appreciated!
Thanks
Hello everyone,
I am trying to simulate collection of nanoparticles in a periodic box using Soft sphere modelling and as nanoparticles have some amount of cohesive force acting between them, I want to use cohesive VanderWall force between them.
please note the spelling: van der Waals
I am done with Simulation without any cohesive force (using pair_style gran hooke). But I was searching on how to use Vanderwall force with this model, I didnt find any potential having this Vanderwall part(only).
what specific functional form are you looking for? there are plenty of options available in LAMMPS. please note, that for some of those potentials, you can turn of parts by using a coefficient of 0.0 for that part. in addition, there is pair style table, which can model about any kind of pairwise additive interaction. you only need to generate a tabulated variant of your potential.
pair_style hybrid will be useful but what other potential should I use alongwith pair_style gran/hooke .
to add a term to the interaction model you need to use pair style hybrid/overlay. with pair style hybrid you can alternate between different pair styles based on the atom type.
axel.
Thanks Axel,
I want to use long range attractive force between particles, which is actually the attractive part of pair_style colloid (Van der Waals attractive force).
I am clear that I want to use -
pair_style hybrid/overlay gran/hooke colloid
pair_coeff * * gran/hooke 9810000.0 0.0 148.0 0.0 0 0
pair_coeff * * colloid 190.0 1.0 10.0 10.0 50.0
But in this case pair_style colloid will include both attactive and repulsive part. I just want attractive part (long range) with linear spring. AND I think in colloid pair style there is no parameter which I can use to switch off the repulsive part.
this only matters, if particles can actually come close enough. other than that, there is always pair style table.
axel.
Do you need the fidelity to model cohesion using the LJ potentials, or can you get away with using one of the bulk material cohesion model in the granular pairstylem, DMT or JKR.
For me in this stage of my work, I don’t need contact cohesion model (i.e JKR or DMT). I want to build a simple system where nanoparticles are attracted by the integrated LJ potential for spherical particles (i.e.attractive part of pair_style colloid).
Where I can give min cutoff, max cutoff, Hamaker constant and radius of the particles as input. This model is there in Mfix, but I am not sure about Lammps, if it is already there or we need to do.
For me in this stage of my work, I don’t need contact cohesion model (i.e JKR or DMT). I want to build a simple system where nanoparticles are attracted by the integrated LJ potential for spherical particles (i.e.attractive part of pair_style colloid).
let me repeat, if you use pair style hybrid/overlay and define your colloid coefficients in such a way, that the minimum of the granular potential coincides with the radius of your particles, then your particles will only ever experience the attractive part of the interaction. if you don’t believe that that can work, you can write out the colloid potential with the pair_write command and change the table so that for all radii shorter than the radius the potential is constant and thus the forces zero, and then use the potential with pair style table.
Where I can give min cutoff, max cutoff, Hamaker constant and radius of the particles as input. This model is there in Mfix, but I am not sure about Lammps, if it is already there or we need to do.
why don’t you try out what has been suggested?
axel.
…and - of course - nobody is stopping you from writing a new pair style that combines the attractive pair of pair style colloid with pair style gran/hooke
axel.
Thanks Axel!
Actually I understood what you said in that mail. I was explaining again to Thomas.
Anyways thanks alot for your continuous support.