In MEAM value why ibar has same equation?

https://docs.lammps.org/pair_meam.html

화면 캡처 2022-07-06 101215

as you can see ‘0’ and ‘4’ have same equation

when i run this potential with ‘0’ ibar, CMD shows error
but run with ‘4’ ibar, it works

why ‘0’ and ‘4’ have same equ and what is difference??

thank you

What error??

I don’t know, perhaps @shuetter does.

P.S.: writing complete sentences and spelling out complete words are much appreciated.

MEAM library file :

‘Fe’ ‘bcc’ 8 26 55.847000
5.027000 3.800000 2.000000 0.900000 1.000000 2.851000 4.280000 0.585000
1.000000 -0.800000 12.300000 2.000000 1.000000 0.000000

‘C’ ‘dia’ 4. 6 12.0111
4.38 4.26 5.00 3.20 3.980 3.567 7.37 1.490
1.0 7.5 1.04 -1.01 1.0 0

error code :

ERROR on proc 0: Not a valid integer number: ‘0.000000’ (src/MEAM/pair_meam.cpp:444)
Last command: pair_coeff * * Fe3C_library_Liyanage_2014.meam Fe C Fe3C_Liyanage_2014.meam Fe C

if i change ibar with 3 or 4, the in file runs well

This line is incorrect and the error message tells you so. ibar is an integer value and thus you must enter an integer number. However, 0.000000 is a floating point number and thus the error message is correct. If you correct the MEAM library file to have a (correct) integer ‘0’ in place of the incorrect ‘0.000000’, LAMMPS will accept it.

If you change it to ‘0’ it also will run.

You have a badly formatted MEAM library file.

If in doubt, read the source (and papers).

ibar <= 0 (so, 0 and -5) use constant G=1.0 for alloys, the others use a mixture rule.

Fun fact: the Gullett/Wagner report states “Common choices for G are (options 0 and 1)”, but most modern uses imply ibar = 3, which is the original equation used by the Baskes/Lee groups.
4 then is “0 but with mixing”, -5 is “0 but with gamma<-1.0 fixed”

1 Like

it runs well

thank you so much!!

thank you very much!!