[lammps-users] Total energy definition

Dear LAMMPS developers and users,

I have a quick question about a definition of total energy in LAMMPS.
Is total energies shown in "log.lammps" file sum of just kinetic and
potential energy?
I am wondering since in my file "TotEng" is increasing even I use nve
ensemble...
Does "fix efield" command affect to the definition of total energy?
It might be very simple question, but I would be so glad if you tell me
anything about this.
Thank you very much.

Best,
Nanako Takahashi

See the doc page for thermo_style. total eng is PE + KE.

If you're applying an efield to your system, then you're
adding energy.

Steve

Dear Steve,

Thank you so much about thermo_style file.
It helps me a lot.

Another quick question, would you tell me how the energy by efield is defined?
In my understanding from your comments, it is adding every time steps.
Is it usual "q*E*x" where q : charge, E : e field, x : distance of an atom between previous step and current step?

Thank you very much.

Best regards,
Nanako

Steve Plimpton wrote:

If you're asking if force times distance is energy, then yes.

Steve

Dear Steve,

Thank you so much for your reply.
So sorry for many questions, but I am still confused by definition of nve and the way of updating energy due to e-field.
If energy by e-field is obtained by force times distance, how the distance is defined?
Since there are potential energy by covalent bonds, it also contributes to coordinate of next step.
So how the distance for energy by e-field is extracted?

And as another question, isn't it possible to update the number of molecule between timestep?
In case of e-field, the total energy is updating even with nve ensemble.
Would you tell me what is the difference between the enery and the number of molecule?
I would appreciate any comments of you.
Thank you very much.

Best,
Nanako Takahashi

Nanako Takahashi wrote:

If you apply an efield to the system you are adding
energy over time. Nothing tracks how much energy this is.

Steve