Please reply to the mailing list, not to individuals, thanks.

If you are confident that the potential and the icosahedral structure
are stable, then the problem must have arised from indentation. Check
the position, rate, and size of the indenter - which is ultimately
your job. I will not have time to debug your script.

Good luck,

Dear Ray
I have found the problem and I have fixed it. Thank you for your attention and your helpful tips.