Nano-indentation by Berkovich Indenter

Dear All,

I am a new user to LAMMPS and I am using the latest LAMMPS version available for windows. I am trying to simulate the nanoindentation of metallic glass material (Ni, Zr, Ti) by a Berkovich shaped diamond indenter. The simplified code I use is attached. Basically what I have done is created a data file of the material, and read it later. Then in that, I build up the indenter geometry with diamond atoms and move it towards the material surface. The issue that I am facing is that the atoms from the material get attracted (as to be expected initially) to the atoms in the indenter. However, then the material atoms seep into the diamond lattice of the indenter in a diffusion like movement which is not desired.

I attempted varying the LJ/cut values, and pair_coeff values of LJ potential. (Both according to research paper data and on my own judgment). It seemed like I was able to vary the extent of the number of atoms that move inside the diamond lattice but is never at an acceptable level (ideally zero). I have also found out that increasing the minimization criteria increases this level of seepage of atoms into the indenter (expectable) and increasing rate of movement of the indenter downwards decreases this seepage/diffusion (agreeable; as there is lesser time for seepage and faster minimization completions). It was also noted that most atoms are pushed away as expected and do result in an impression on the material surface. Additionally, the indenters available in LAMMPS (sphere, etc.) work as expected and make the relevant impressions on the surface as needed.

Firstly, Can someone with relevant knowledge suggest a method to solve this issue?

Secondly, what is the command/method used to create a region that would repel all atoms that work like the stock indenters available by fix indent command?

Thank you very much.

code.lmp (1.98 KB)

your settings and parameters for the lj/cut potential make no physical sense for the chosen units. where did you get them from? how did you compute/convert them?
your interaction energy is huge for eV as energy unit and your diameter is tiny for Angstrom as length unit. no wonder atoms are massively attracted by the indenter and can pass through it.

also your neighbor list settings with “every 50” is not a good choice.

i cannot say much about the rest of the input. it is too confusing for me.