Problem with group-ID in fix ordern

[JiaYuanChng]

Hello,

Firstly thank you for developing this plugin for lammps.

The examples run the compute position command for all molecules in the system, along with the fix ordern command for all molecules. Specifically,

compute positions all position
fix f3 all ordern diffusivity 1000 100000 c_positions nb 10 nbe 25 file diffself.dat diffonsag.dat

If one is only interested to compute the position of a specific group of molecules (eg. methanol molecules in this example) and thence the ordern properties of those molecules, the commands will be modified into:

group met type 4      # The Oxygen of METHANOL molecules`
...
compute positions met position
fix f3 met ordern diffusivity 1000 100000 c_positions nb 10 nbe 25 file diffself.dat diffonsag.dat

The former ran perfectly well with the output file reading:

#NOTE: MSDs have been divided by the factor 6 (or 2, i.e., MSD_x, MSD_y, and MSD_z).
#Time	MSD__met	MSD__wat	
 1000 343.045 321.968
 2000 537.739 516.801
 3000 712.744 694.751
 4000 879.662 865.619
 5000 1042.65 1032.98
 6000 1203.51 1198.95
 7000 1363.04 1364.06
 8000 1521.98 1528.54
 9000 1679.9 1692.4
 10000 1837.2 1855.64
 11000 1993.85 2018.14
 12000 2150.07 2180.28
...

After that modification, the execution stopped when the fix ordern is invoked. No specific error was written in the log file or output files to allow troubleshooting myself.

Thank you.

Best wishes,
JY