pair_coeff error

Hello everybody

lately I faced an error with pair_coeff command : ( “ERROR: Expected floating point parameter in input script or data file (…/pair_lj_cut_coul_long.cpp:630)” )

here is my script:
units real
atom_style full
special_bonds lj/coul 0.0 0.0 0.0
pair_style lj/cut/coul/long 10.0 9
bond_style harmonic
angle_style harmonic
kspace_style pppm 0.0001


pair_coeff 1 1 lj/cut/coul/long 0.1553 3.166 #O-O
pair_coeff 2 2 lj/cut/coul/long 0.0 0.0 #H-H
pair_coeff 1 2 lj/cut/coul/long 0.0 0.0 #O-H
pair_coeff 3 3 lj/cut/coul/long 0.0564 3.214 #c-c
pair_coeff 3 1 lj/cut/coul/long 0.114 3.28 #c-o
pair_coeff 3 2 lj/cut/coul/long 0.0 3.28 #c-H

bond_coeff 1 1000 1.0
angle_coeff 1 100 109.47

group spce type 1 2
group Cgraphene type 3

fix sheet Cgraphene setforce 0.0 0.0 0.0

I don’t understand the meaning of “floating point”. I got my data file from lammps with write_data command. Is it possible that the problem comes up from my datafile?. I will appreciate to help me solve this problem.

thank you


Check wether you need to mention “lj/cut/coul/long” statements for the pair coefficients in the input file or not.
Also check it for the bond_coefficients and angle_coefficients, wether you need to mention the style again or not.


There are two problems with your input script. If you don’t use pair hybrid or hybrid/overlay you mustn’t use the name of pair style in pair_coeff lines. See the examples at:
The second problem is that in pair_coeff the first atom type must have lower (or equal) number than the second one. More: