Format of the Data File

Dear LAMMPS Users,

Hello. This is Masato Koizumi, and I am currently simulating polymer chain deformation using quartic bonds. My input script reads a data file where a portion of the file display the following:

1 atom types
2 bond types

0.0000 158.5000 xlo xhi
0.0000 158.5000 ylo yhi
0.0000 100.0000 zlo zhi


1 1

Pair Coeffs

1 1 1

Bond Coeffs # quartic

2 1200 -0.55 0.25 1.3 34.6878

However, I am obtaining an error that states: Unexpected end of data file (…/read_data.cpp:821)

I would greatly appreciate if someone could provide me with a feedback on the format of my data file. Thank you.


Masato Koizumi

Dear Masato,
Please see the examples in lammps page or github. You should define your bonds.

Dear Hossein,

Thank you for your reply. Could you refer me to the LAMMPS examples or github you are discussing. I am searching the LAMMPS examples that I came in with the package but could not find the one that I am looking for in regards to defining bonds. Thank you.


Masato Koizumi

the canonical source for the definition of the file format is the
documentation for the read_data command. everything about the data
file format is included there.

it is near impossible to give meaningful advice based on such limited
information provided. please follow the guidelines listed here:
most important: always report your LAMMPS version and platform, and if
you provide inputs, provide complete inputs. if your input/data files
are large or complex, create a small example input that have just
enough commands and atoms to reproduce the error you are seeing.
remember, the more effort it takes to understand what you are doing,
the less likely you are to get help, let alone good help.

there is one very obvious inconsistency here: you state, that you have
2 bond types, but your Bond Coeffs section only defines parameters for
one of them. that cannot work.


The examples dir, has sample data files for some

problems. E.g. examples/micelle/data.micelle.


Also, there’s a really old web page that does a great job of explaining the basics of the DATA file format here:

The “read_data” docs page Axel mentioned is comprehensive. It is like a reference manual. Whatever information you need is in there somewhere. But I found the page above to be a good place to start.