# Set kinetic energy of each atom

Hi, all lammps user,

I am using lammps to simulate the laser energy depositing into nanoparticles. The laser energy is spatially-dependent since the plasma resonance, and time-dependent in gaussian function. I am trying to add kinetic energy to each atom to simulate the spatially-dependent energy depositing, and apply the kitnetic energy in gaussian function to simulate the time-dependent depositing. Does anyone could tell me how to do this? I have read the m****anual and searched the mail list, but I am still confused.

Best regards,

Jacobi

have you looked at fix ttm or fix ttm/mod? those seem to be related to what you are describing.

otherwise, you could look into using the “velocity set” command with atom-style variables, where you could define a formula, that will compute the added velocity based on the individual atom’s position. with the “sum yes” option, that velocity would be added to the existing velocity.

axel.

I have looked at fix ttm or fix ttm/mod, but it seem doesn’t meet my needs. In my case, I have caculated the power of laser at each atom site (I cannot define a formula, because it is tabular data). I am trying to apply those data to MD. I assume the atom gain all energy of incident laser, and transfer to it’s kitnetic. So, What I am going to do is changeing the kienetic energy of each atom to the tabular data. Does any command in lammps can do that?

Jacobi

I have looked at fix ttm or fix ttm/mod, but it seem doesn’t meet my needs. In my case, I have caculated the power of laser at each atom site (I cannot define a formula, because it is tabular data). I am trying to apply those data to MD. I assume the atom gain all energy of incident laser, and transfer to it’s kitnetic. So, What I am going to do is changeing the kienetic energy of each atom to the tabular data. Does any command in lammps can do that?

none, that i know of.

axel.

You could certainly write your own fix to modify atom velocities however you wish.
Including reading in a tabulated file of velocities or other info that allows you
to compute velocities. If you really have files of KE deltas for every atom
at different timesteps, then you could probably define a new per-atom KE-delta
value with the fix property/atom command, read them in with “read_data” commands
from data files that contained only those values, and then write a small fix to reset
the velocity of each atom, based on the KE-delta value.

Steve