👉 In crystallography, a solid whose atoms are arranged in a plane with one of its faces parallel to this plane. This means that all atoms have the same number and type of electrons on each side of the plane. Hollow crystals (also known as cubic or monoclinic) have three different types of planes, and these planes can be aligned in any order. When they are aligned in a particular way, the crystal has a set of reciprocal lattice vectors that specify the directions in which
