Dear LAMMPS users,

My problem is with the development of a new potential in lammps, I have written a pair style and tied to compare the total forces coming from the interactions for a snapshot of atoms(per unit cell of MgO) which I had done the manual calculations. But there is a difference in the values, I observed the difference is not from the force formulas of the potential I have included but from the number of interactions happening.

For the system of MgO it has 3 atoms per unit cell and hence theatricality only 9 interactions has to happen, but in lammps I could see a more than a 100 interactions happening, could I know the reason, if so how could I control it ??

Regards,

Srinivasan

Dear LAMMPS users,

My problem is with the development of a new potential in lammps, I have

written a pair style and tied to compare the total forces coming from the

interactions for a snapshot of atoms(per unit cell of MgO) which I had done

the manual calculations. But there is a difference in the values, I observed

the difference is not from the force formulas of the potential I have

included but from the number of interactions happening.

For the system of MgO it has 3 atoms per unit cell and hence theatricality

only 9 interactions has to happen, but in lammps I could see a more than a

100 interactions happening, could I know the reason, if so how could I

control it ??

have you ever heard of periodic boundary conditions?

Oh, I think I do. For a box of 4.212 x 4.212 x 4.212 with just contains three ions at 0,0,0; 2.106,2.106,2.106; and 2.206,2.206,2.206, what is the problem of the periodic boundary conditions. Also I tried to keep the cut off big

enough(10 A) to have all the interaction.

Regards,

Srinivasan

Oh, I think I do. For a box of 4.212 x 4.212 x 4.212 with just contains

three ions at 0,0,0; 2.106,2.106,2.106; and 2.206,2.206,2.206, what is the

problem of the periodic boundary conditions. Also I tried to keep the cut

off big

enough(10 A) to have all the interaction.

there is no problems with PBC except that you don't seem to be

considering them correctly in your "only 9 interactions" claim.

No no, I did not claim that only 9 interactions, the worst case without even considering the action and reaction, number of times the looping occur could be 9.

Pair style I created is simple, that is I have took the Buckingham potential and the wolf summation from the exsisting lammps code and in addition I included a harmonic term, the forces resulting from the harmonic term is as expected but I could not control the other two potentials.

No no, I did not claim that only 9 interactions, the worst case without even considering the action and reaction, number of times the looping occur could be 9.

But that is obviously wrong. You donâ€™t provide much useful information to prove it to you. It looks like you seem to be incorrectly assuming minimum image conventions, with too large a cutoff. Also your implementation seems to be inconsistent. On top of that, these are all available potentials, and there is no immediate need to program your own pair style.