[EXTERNAL] Re: BOP potential for carbon

Do not modify anything including cutoff. If you do not have cu, fine, just do not define cu in your configuration. Again, please test a simple bulk crystal and compare the results with paper. There is no point to test anything else at this point. Note also that the BOP has been widely used in much stringent simulations like solidification and thin film growth.


As I wrote in my email, I repeated all the tests (and the energy minimization also) have been perfomed with the original NON-MODIFIED potential file, taking a cutoff for the ghost atoms equal to 12.0 A. This is the first thing I have done when I saw these strange results in my calculations.

The material properties calculated and listed in the pdf “results_2.pdf” are also calculated with the original potential file.


Do you have abnormal values before relaxation? If so, Can you limit the size that atoms can move during each minimization step?

There are two couples of atoms for which:

  • before relaxation the interatomic forces are abnormally high (> 10 000 000 Ev/a) but the per-atom energy relativelyl low (8.3 eV), which sounds strange
  • after relaxation, forces are still abnormal (> 10 eV/A) and the per-atom energy totally out of range ( -3700 eV)

Yes, it is possible to limit atomic displacements during energy minimization. I limit the displacements to < 0.1 A but the results do no change. Moreover, after relaxation, these atoms for which I have abnormal force and energy values have hardly moved ( less than 0.01 A) with respect to their positions before relaxation (see also the pdf results_2.pdf) i.e. the local configuration is almost unchanged.