When I speak about atoms with respect to crystals and crystallization, I mean the crystal constituents that (are going to) occupy the lattice locations (points) of the crystal. These could be atoms, but also ions, and also molecules (compounds of atoms). A lattice point can also sometimes not coincide with the position of a single atom. In that case the lattice point is just the location of a pattern of atoms, like a complex ion. The constituents of such a local pattern then can be grouped around the lattice point. In this way the lattice points are geometrical points which reflect the ordering of the crystal constituents.
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