Hi,

This may be a bit off the mark question. However, your insights will definitely help to resolve the issue.

The lj/smooth/linear in lammps (http://lammps.sandia.gov/doc/pair_lj_smooth_linear.html) gives the expression for energy. The explicit expression for the energy comes out to be as mentioned in eqn(3) of the attached pdf file.

I calculate the potential energy using this expression for a given configuration using my own code. Then I calculate the same using lammps’ inherent function pe for the same configuration.

There is a difference of ~0.12 between the potential energy values obtained from these two approaches.

Does the energy expression for lammps include or exclude any extra term?

Please provide your valuable comments.

Thanks & regards

Pranab

pot_en_exp.pdf (62.1 KB)

Hi,

This may be a bit off the mark question. However, your insights will

definitely help to resolve the issue.

The lj/smooth/linear in lammps

(http://lammps.sandia.gov/doc/pair_lj_smooth_linear.html) gives the

expression for energy. The explicit expression for the energy comes out to

be as mentioned in eqn(3) of the attached pdf file.

I calculate the potential energy using this expression for a given

configuration using my own code. Then I calculate the same using lammps'

inherent function pe for the same configuration.

There is a difference of ~0.12 between the potential energy values obtained

from these two approaches.

Does the energy expression for lammps include or exclude any extra term?

how on earth should anybody but you know what you are comparing here?

nobody but you knows what kind of system you are comparing or even

what units you are using. how can we know that this difference is not

simply due to truncation errors when reading/generating coordinate

information.

what LAMMPS computes is in the source code. if that doesn't match what

is in the documentation says, please point it out to us. but don't

expect anybody here to have a crystal ball and tell you what is

causing the difference without knowing anything about what you are

comparing.

axel.