vol keyword in thermo style and pbc

Hello everyone,

I have a doubt in the way how volume is calculated or which volume it refers to. There was no mention of what it refers to in the manual. However, if I assume it is the volume of the molecule(s) I gave has input(using some mechanism), then I cannot comprehend the following :

The molecule is inside periodic boundary condition. By no way or procedure the molecule can have a volume larger than the pbc box (as the molecules fragment enters from the other side inside the box). However, in one of the simulations I was carrying out I noticed that when I used thermo_style multi, the volume I got in my log file was greater than the volume of the pbc box.

Can anyone please suggest by what mechanism is the volume in lammps calculated and also clarify my doubt? I shall be grateful for it.


Sonu Kumar

3rd Year, B’Tech in Chemical Engineering