Hi

I want to calculate the electrostatic interactions energy between two groups of particles. Thus, I have used two commands in my input script

Pair_style lj/cut/coul/long 12 12

Pair_modify lj/cut compute no (or mix arithmetic compute no)

Kspace_style pppm 0.0001

As we know, pair energy = evdw+elong+ecoul and electrostatic energy = elong + ecoul. In this case, as I am omitting the vdw interaction energy by pair_modify lj/cut compute no , is it only calculating the electrostatic energy? Or to calculate the only electrostatic energy i should use this command: pair_style mix arithmetic compute no? Please advise.

If I do simulation only with pair_style coul/long 12, i am getting error like this-

PPPM initialization …

using 12-bit tables for long-range coulomb (src/kspace.cpp:321)

G vector (1/distance) = 0.20238

grid = 24 24 30

stencil order = 6

estimated absolute RMS force accuracy = 0.00899096

estimated relative force accuracy = 2.7076e-05

using double precision FFTs

3d grid and FFT values/proc = 12958 4608

ERROR: All pair coeffs are not set (src/pair.cpp:225)

Last command: run 50000