Effective mass and DLVO


I know that the damping term can be switched on and off, but can I also switch the effective mass on and off in LAMMPS? The page I’m referring to is:


Is it also possible to use the DLVO potential for electrostatic/van der Waals cohesion or the Lennard-Jones style van der Waals potential with the GRANULAR package in LAMMPS? It looks like it is only available with the COLLOID package:


Kind regards,


I don’t know what you mean by “switch the effective mass off”.

It’s in the eqs for a granular pair style, meaning it is

computed internally as part of the model.

Re: DLV0, I think it is possible to use DLVO = pair colloid + pair yukawa/colloid

together with a granular potential via pair_hybrid. I’m CCing

Dan Bolintineanu to see if he agrees or thinks that makes sense.

Note that pair yukawa/colloid requires all atoms of the

same type have the same size (error if not), so you couldn’t

do a general polydisperse system (every particle has different size),

like you could with a granular system. Also I think you would

need to insure the particle sizes specified with pair colloid (also per-type)

were consistent with the particle radii.


Steve, Andrew,

Agreed with everything Steve said.

Granular for short-range repulsion and colloid/yukawa for long-range seems reasonable, but it’s hard to say without knowing more about your physical system. If you’re looking to add cohesion to granular particles, a more appropriate physical model might be JKR or DMT. These basically add an attractive force to the granular contact force (with a non-hysteretic component in JKR). Colloid and yukawa are both somewhat long range (i.e. they act only when particles are not in contact), and they typically only apply in certain regimes of particles suspended in solvent. There’s some interesting new literature suggesting that even for certain dry powders, both cohesive contact (e.g. JKR/DMT) and long-range attractive forces are important, see e.g Parteli et al, Nature Scientific Reports, DOI: 10.1038/srep06227.

I have a working version of a couple of JKR/DMT pair styles with some additional features (rolling and twisting friction, different damping models). They’re still in testing, eventually we’re hoping to add them as options to the granular package. Send me an email if you’re interested in trying these out, I’d be happy to have somebody else run some tests.

Dan Bolintineanu