simulation gold nano particles in water

Dear all
I have some question about simulation gold nano particles in water solvent ,I would appreciate if you could answer me.

  1. When I use metal(mass = grams/mole) as units, which mass should I use in order to determine the mass of gold (colloid) in data file?
    1: atomic mass 196.96654 (gr/mole)

2: total mass of gold sphere (colloid ) >>> 4pir^3/3*density
Do you suggest other units for colloidal system? such as si? Is using metal incorrect for colloidal system? I have not good sense about using (gr/mole) for colloid sphere.

  1. Do epsilon-nn(Au nano particel - Au nano particle) which was used in colloid potential,have the same value for all of colloids with radius equal 5sigma or 10sigma or 20sigma ? Is that value equal epsilon factor for gold atoms in LJ potential(0.351 Angestrom)? If no, How we can find it for colloids?quantum !!!?
    I have this question about sigma too.
    *** Ann = 4π^2εnnρ1ρ2σnn^6 ***

3)For define water’s atoms in data file, I have used from full style: atom-ID molecule-ID atom-type q x y z
I know we can’t use two data file in lammps and I have one or more gold sphere as nano particles that I have to define coordinates of sphere’s center with that style(full),but they are not molecule and they have not any charge!!! what should I do?

Thanks in advance.


your first 2 Qs are about how to define your model. That
is not a LAMMPS Q, that is a question you have to figure out.
You can use any units that LAMMPS supports, so long as
you are consistent.

Your last Q is about having 2 types of particles. Whatever
atom style you use, it should have all the attributes you
need for both kinds of particles. E.g. if some particles
have charge, then use an atom style that stores charge.
It is OK if some (or most) of the particles you define
have a value of 0.0 for charge. The doc page for the
read_data command describes the format of the data
file for every atom style, including atom_style hybrid.