If you dump with group all you should have one line per atom
in the system at that timestep.
Steve
The number of atoms/particles in the system is constant during Widom insertions and it is equal to the initial number of atoms/particles before attempting any Widom insertion. You are still in an N-V(or P)-T(or E) statistical ensemble. This is in contrast to grand canonical monte carlo where the number of particles in the system is allowed to fluctuate. If you include in the “thermo_style” command the argument “atoms” you will see that the number of particles/atoms is indeed constant.
The main idea behind Widom insertion is to place a test molecule/atom in several spatial locations of the simulation box, compute the energy of inserting the test molecule/atom in the system and then estimate the excess chemical potential based on a suitable average of the energy of insertion. See for instance https://en.wikipedia.org/wiki/Widom_insertion_method for more details.
Hope it helps
Evangelos
Στις Παρ, 4 Δεκ 2020 στις 8:53 μ.μ., ο/η Steve Plimpton <[email protected]> έγραψε: