Hello LAMMPS users,
I have a question in regards to the method to implement ewald sums for rigid molecules. How would one implement ewald sums with no intramolecular interactions(VdW,electrostatics) while also not excluding interactions with the same molecule with its periodic image of rigid bodies?
I am currently using lj/cut/coul/long coupled with kspace_style ewald and get this warning:
"WARNING: Neighbor exclusions used with KSpace solver may give inconsistent Coulombic energies (../neighbor.cpp:441)”
Which If I believe is coming from "neigh_modify exclude molecule" command I am using to turn off interactions within the molecule.
Any insight into this would be much appreciated. (using August 15,2015 LAMMPS version)
Thanks,
Michael Goytia
Hello LAMMPS users,
I have a question in regards to the method to implement ewald sums for rigid molecules. How would one implement ewald sums with no intramolecular interactions(VdW,electrostatics) while also not excluding interactions with the same molecule with its periodic image of rigid bodies?
I am currently using lj/cut/coul/long coupled with kspace_style ewald and get this warning:
"WARNING: Neighbor exclusions used with KSpace solver may give inconsistent Coulombic energies (../neighbor.cpp:441)”
Which If I believe is coming from "neigh_modify exclude molecule" command I am using to turn off interactions within the molecule.
Any insight into this would be much appreciated. (using August 15,2015 LAMMPS version)
please recall, that with a kspace solver, pairwise coulomb
interactions are computed in two parts. one part in real space as a
damped pairwise coulomb and the other using a lattice sum or an
approximation of it, which would compute the missing part. now, if you
simply exclude the real space part for an excluded pair, you only
remove the damped coulomb, but not the corresponding contribution in
k-space. thus excluded pairs are handled by *including* the damped
interaction and then *subtracting* the full, undamped pairwise coulomb
for that pair. for rigid molecules, this should have no impact on the
forces, but you still have inconsistent energies.
axel.