Dear LAMMPS users and developers,
I am trying to compute the average velocity of a substance that is composed of 2 molecules. For this purpose, I am using 2 different methods:
1- Computing the kinetic energy of the substance with the command :
compute KinEn substance ke
Then, calculating the velocity with : v= sqrt(2E/m) , where m is the mass of the substance.
2- Computing the velocity directly with vcm/chunk command as follows:
compute cc1 substance chunk/atom molecule
compute myChunk substance vcm/chunk cc1
Then, I print the results with:
thermo_style custom step c_KinEN c_myChunk c_myChunk c_myChunk c_myChunk c_myChunk c_myChunk
However, the results that I obtain with the 2 methods are very different !
Therefore, I would like to ask you if there is something wrong with my code or if there is a concept in the vcm/chunk method that I am misunderstanding.