questions about yukawa/colloid pair coeff

Hello users,

I have two questions about how to define the pair_coeff of yukawa/colloid. In the manual, A is able to be calculated by an equation at low surface potential, i.e. less than 25 mV. Should I also use this equation at higher surface potential, say -70mV? Or there is another equation for higher surface potential?

Besides, during the calculation, is this “surface potential” value just absolute value or including positive/negative signs? Thanks so much.

Jing

I don’t know the answer to that, which is really a conceptual
Q, not a LAMMPS Q.

Randy (CCd) may possibly know.

Steve

Jing,

This is just a bound for which approximation should hold, namely the Debye-Huckel or Gouy Chapman theory for double layers. You can find these in any surface science/chemistry book. I suggest Israelachvili’s book

“Intermolecular and Surface Forces” or Heimenz and Rajagopalan’s “Principles of Colloid and Surface Chemistry.” In principal you will find that these double layers actually are even more complicated than these approximations. Best clue I can give you is do some reading.

I second eric suggestions. At higher potentials, there are some terms in the original equation (See Israelachvili’s book) and the references he refers to which can’t be neglected. I suggest looking at the original references.

Hope this helps.

Regards,
Vikas

Thank you all so much. Your suggestions are very helpful.

Jing