direction. For the 1D case shown in Fig. , to calculate energies and forces on atoms in the third cell (yellow), other cells are considered in the forward (+ x) and reverse (-x) directions. In the forward wrap-around, the first two cells belong to the α 4 group as they are padded to the last cell. In 3D, to translate a cell by a vector ⃗ R, the corresponding Q-factor Q b mn for atoms in the cell is multiplied by e 2iαζ s n tm • ⃗ R (Eq. 15) and the structure factor S C mn is multiplied by e -2iαζ s n tm • ⃗ R (Eq. 16). Here, the translation vector is ⃗ R = u x R x x +u y R y ŷ +u z R z ẑ, with {R x , R y , R z } corresponding to the (orthorhombic) box dimension and u j ( j = x, y, z) are 0 or ±1 but not simultaneously 0, to cover the 26 neighboring images of the simulation box. In the 1D case for the x-direction, u x = ±1 handles the forward and reverse wrap-arounds. Thus, for each α group, the wrap-around factor