To print out Center of Mass coordinates using FIX/AVE

Hello All,

I am trying to print out COM coordinates by using the following fix

fix com 2 ave/time 1 1 1 f_2[1] f_2[2] f_2[3] f_2[13] f_2[14] f_2[15] file

All I need in my current work is to print out these values at a non-linear (exponential) timesteps, i.e. Nfreq should not be a constant value. Is this possible to do in LAMMPS or is there any other way to output COM data (coordinates and image flags) using a dump command so that I can use dump_modify every $s to specify at what all timesteps I want my output.

Thanking You ,

With regards,