A bug occurred when export to lammps data file

Sailang · November 13, 2025, 11:07am

Hi,

For the latest ovito (actually also for the recent ovito versions), when I export a file to lammps data,

the file will look like

# LAMMPS data file written by OVITO Pro 3.14.1

16573 atoms
4 atom types

60.9763723175 0.0 0.0 avec
0.0 61.0008627877 0.0 bvec
0.0 0.0 59.9828566258 cvec
0.9616840196 0.9485835072 80.0149758206 abc origin

However, it should be like

# LAMMPS data file via write_data, version 29 Aug 2024, timestep = 1470000, units = metal

42000 atoms
4 atom types

0.9477354616024852 61.952264538398126 xlo xhi
0.9477354616024852 61.952264538398126 ylo yhi
2.371598754472661 155.02840124552972 zlo zhi

Pls check it.

Thank you very much!

BR,
Sailang

utt · November 13, 2025, 11:33am

This is not a bug. Both formats are valid LAMMPS data files, as documented in the LAMMPS manual.

The first output format you are seeing is the restricted triclinic simulation cell format. You can select it using this checkbox in the data export settings:

A data file written in this format will look like this:

# LAMMPS data file written by OVITO Pro 3.14.1

25 atoms
2 atom types

22.0 0.0 0.0 avec
0.0 22.0 0.0 bvec
0.0 0.0 22.0 cvec
0.0 0.0 0.0 abc origin
...

If you uncheck the option, OVITO will produce the other format:

# LAMMPS data file written by OVITO Pro 3.14.1

25 atoms
2 atom types

0.0 22.0 xlo xhi
0.0 22.0 ylo yhi
0.0 22.0 zlo zhi
...

Sailang · November 13, 2025, 2:00pm

I see! Thank you very much!

BR,
Fan

utt · November 17, 2025, 1:21pm

I checked your files and even the unit/super cells are not recognized as HCP phase by OVITO. What c/a ratio does your material have? OVITO usually expects a c/a ratio reasonably close to the ideal 1.63. Are you sure you handled the rotation and cutting of your unit cell correctly?

Ying_Zhang · November 17, 2025, 3:42pm

Maybe your respond the post ?

The material’s a is 4.709 Å and c is 7.442 Å. c/a is1.5804. I am sure the rotation and cutting is correct.