[lammps-users] parameters for Lennard jones potential.

Dear fellows,

I would like to know \epsilon (depth of the potential) and
\sigma(intermolcular distance) for Lennard Jones potential
for Mg(Magnesium), Cl(chloride), SO4(sulfate), PO4(phosphate).
Those atoms are inside my box.
Do you know where I can find these values ?
Pairs : Mg-Mg, Mg-Cl,Mg-PO4, Cl-Cl,Cl-PO4,PO4-PO4
                  Mg-SO4, SO4-SO4, SO4-PO4.
I don't know where I should find out these values.
Thank you.

I'd google for this or use a scientific paper database. There
are tables of these kinds of params.