A reference implementation for Ewald summation, which calculates the electrostatic energy of a periodic system.

• Support for charges and dipoles.
• Support for sheared volumes.
• Tin foil boundary conditions.
• Errors can be controlled to order $10^{-12}$.

Calculate the Madelung constant for NaCl using its primitive cell.

import Ewalder

latvecs = [[1,1,0], [1,0,1], [0,1,1]]
pos = [[0,0,0], [1,1,1]]
charges = [1, -1]
sys = Ewalder.System(; latvecs, pos)
E = Ewalder.energy(sys; charges)
@assert E ≈ -1.74756459

For more explanation, see the package documentation.

Usage examples are contained in Ewalder/test.