I am calculating the energy of my sample for different temperatures and I would like to know, for a given atom, the interatomic forces for each temperature. Do the interatomic forces change with different temperatures? How can I extract that information from LAMMPS?

Thanks.

I am calculating the energy of my sample for different temperatures and I

what "energy"? there are all kinds of energies.

would like to know, for a given atom, the interatomic forces for each

temperature. Do the interatomic forces change with different temperatures?

for normal simulations forces only depend on the relative positions of

the atoms. please see the corresponding potential functions.

How can I extract that information from LAMMPS?

forces on each atom can be output in custom style dumps as fx, fy and

fz properties.

axel.

Almost all pair styles in LAMMPS depend only

on the coords of atoms, not their velocities (where

velocities are affected by temperature). Exceptions

are granular pair styles and DPD.

Of course if you run a system at a higher temp,

the atoms will move differently, which will lead

to different coords and forces.

Steve

Hello,

I know that for a given interatomic potential, the interatomic forces only

depend on the positions. Also I know that for a certain temperature, doing

NVE, by using a thermostat you can introduce in the system a dynamical

variable that represents the friction in the sistem until the temperature is

equal to the desired value, where this dynamical variable is related to the velocity of the praticle.

I want to know if you can extract that, the complete term in the right side

of the Newton equation (interatomic force + friction term), so I get a force

depending on the temperature.

Thanks in advance.

All the thermostat fixes (e.g. nvt, langevin) have extra quantities

they calculate and output about the energy they are adding/subtracting

to the system). See their doc pages.

Steve

Hello,

I know that for a given interatomic potential, the interatomic forces only

depend on the positions. Also I know that for a certain temperature, doing

NVE, by using a thermostat you can introduce in the system a dynamical

variable that represents the friction in the sistem until the temperature is

equal to the desired value, where this dynamical variable is related to the

velocity of the praticle.

so you are talking about a langevin thermostat here, right?

not all thermostat algorithms work this way and for a system in

equilibrium, those terms should usually be small and cancel out on

average.

I want to know if you can extract that, the complete term in the right side

of the Newton equation (interatomic force + friction term), so I get a force

depending on the temperature.

for langevin, you have *two* additional terms to consider, a friction

term and a random term.

both of them are included in the forces output in custom dumps (as are

any other force manipulations due to fixes).

axel.