[lammps-users] About force constant in fix_indent command

Hi all,
As described in LAMMPS manual, the force constant is in force/distance^2 units. However, it doesn’t give the accurate defintion. For a given material, force constant should be specified. Is it something like elastic constant? If not, how can I calculate or look for it?

thanks
Qingjie

Because lammps uses different unit systems, such as metal, real, lj,
etc. This just means the actual unit of the force constant depends on
the unit system you are choosing.

AC

Thanks. I mean the force constant has a unit like elastic modulus, so is the definition for force constant something like elastic modulus? In other words, how to get the specified value of force constant for a given material?

2010/8/16 Albert Cao <[email protected]…24…>

Qingjie,

Sorry for misunderstanding your Q. The force constant describes the
force between the indenter and the substrate. It is not a material
property like elastic modulus and it depends on what you want perform.
If you want to know the meaningful value range of that, you'd look for
some papers on this. Usually, sth like 3.0 nN Å-2 would be a good
choice for metals like diamond (indenter) with Cu (substrate).

Also you will find this literature useful:

Kelchner C L, Plimpton S J and Hamilton J C 1998 Dislocation
nucleation and defect structure during surface indentation Phys. Rev.
B 58 11085-8

Good luck,

Ajing

Thank you very much!

2010/8/16 Albert Cao <[email protected]…24…>