[lammps-users] Fix indent command

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1

Dear LAMMPS Users;

I am currently using fix "indent command" in my simulations. The
simulations work fine and I think the force exerted on system should
be evaluated as: F = -k(r-R), where k is the force constant of
indenter, r is the final position of indenter, and R is the initial
position. However, when I see the lammps documentation webpage
(http://lammps.sandia.gov/doc/fix_indent.html : UNDER DESCRIPTION), it
says lammps calculates the force as: F = -k(r-R)^2. I am wondering why
there is power 2 for r-R term. Is it a typo on the webpage or lammps
calculates force in s different way or I am making some mistake.
Please let me know the exact procedure of evaluating the force in
lammps for fix indenter command.

Thank You

Best Regards

2

it says lammps calculates the force as: F = -k(r-R)^2. I am wondering why
there is power 2 for r-R term.

Because it's a good model for some materials and indenters.
See, for example:
Dislocation nucleation and defect structure during surface indentation
Author(s): Kelchner, CL; Plimpton, SJ; Hamilton, JC
Source: PHYSICAL REVIEW B Volume: 58 Issue: 17 Pages:
11085-11088 Published: NOV 1 1998

LAMMPS computes what the doc page says. If you want something
different, they you would have to change the code. You have the source
code: src/fix_indent.cpp so it would be easy to do.

Steve