EWALD Summation

Dear All,

Can anyone clarify whether lammps uses 3-d Ewald summation (EW3D) or 3-d Ewald summation Corrected (EW3DC) to calculate long-range coloumbic forces?


I’m not sure what you mean by Corrected (EW3DC). LAMMPS uses a standard 3D Ewald sum, unless you are using a slab 2D geometry, in which case the Ewald sum is corrected for the inter-slab interactions. Is that what you mean?


Thanks, Stan.

Yes, you are right; I am using a confined system with PPF boundary conditions. Under such conditions, we need to use the EW3DC proposed by Yeh and Berkowitz (Yeh and Berkowitz, J Chem Phys, 111, 3155 (1999)). They suggested two corrections terms be incorporated while calculating the long-range coloumbic forces, viz., slab correction term and force correction term. In the lammps docs, only the slab correction term is mentioned which made me confused about the implementation of the force correction term. But, after going through the source code ewald.cpp it is clear that lammps has implemented the force correction term also, hence basically lammps is using ED3DC under confined conditions.