[lammps-users] Rewritting the universal equation used in MEAM?

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1

Hi, all
I am now using MEAM in lammps. When calculating the pair potential for element, lammps calculates the total energy of the reference structure as

E=-E0* { 1+a(rij) }* exp{-a(rij)}

I wonder whether I can rewrite this equation with the other universal equation proposed by Rose ( Phys Rev.B (1984) ) with two more adjustable parameters?? How to do this modification?

Thanks a lot!
Yi

2

Hi Yi,
Lammps does calculate

erose = -Ec*(1+astar+(-attrac+repuls/r)*(astar**3))*exp(-astar)

in meam_setup_done.F

Rutuparna

3

If you want to rewrite a MEAM formula, then you'd look
in the MEAM source code, which is in lib/meam

Steve

4

Thanks a lot! Rutuparna and Steve,

I’ve found the equation in meam_setup_done.f

one more question, how can I just change the value of ‘attrac’ and ‘repuls’ parameters?
Is it the only way that I input them in the ‘meam_setup_global.f’, where the defaults of these two parameters are zero

Thanks again for your help!

Yi

5

Oh, sorry , i checked the help documents again and now know how to change these two values
Sorry to bother you all

Yi