[lammps-users] stress about MEAM alloy

Hi all,
    I'm working on the alloy MEAM.
    In order to do that, first I used the "meam" with Si-C alloy in
"example" folder.
    And the Si-C DIAMOND structure is the simulation system.
    All the parameters of SiC.meam are not changed.
    Minimization seems correct, and the final structure are very close
to the castep calculation.
    But when I calculate the elastic constants of SiC.
    The values are very small, like 1e-5GPa.
    I analysed the log file. When displacing the system with small
strain, the stress are too small.
    So the elastic constants are not correct.
    Currently I think maybe the stress of MEAM alloy is not correct.
    Any suggestion?

The parameters in the example file come, I think, from the reference by Huang et al., Modelling Simul. Mater. Sci. Eng. 3:615-627 (1995). That paper shows that the elastic constants are well-fit by the MEAM potential, and in fact the bulk modulus should be an exact fit because of the form of the MEAM potential. So the stresses should be correct.

Is it possible that the problem is with units?

Regards,
Greg

Greg Wagner
Sandia National Laboratories
P.O. Box 969 MS 9409 Livermore, CA 94551
Tel: (925) 294-2180 Fax: (925) 294-3410
Email: [email protected]