Unit-cell stack

FIGURE 5.40 Bill ions of unit cells stack together to recreate the smooth faces of the crystal of sodium chloride seen in this micrograph. The first inset shows some of... 

FIGURE 5.42 The repetition of the cesium chloride unit cell recreates the entire crystal. This view is from one side of the crystal and shows several unit cells stacked together. 

Views of the iron crystal (a) A molecular view, with the lattice representation (b) the unit cell (c) six unit cells stacked to form part of the crystal. 

FIGURE 10.22 Geometries of (a) primitive-cubic and (b) body-centered cubic unit cells in both a skeletal view (top) and a space-filling view (bottom). Part (c) shows how eight primitive-cubic unit cells stack together to share a common corner. 

The lines in the figure divide the crystal into identical unit cells. The array of points at the corners or vertices of unit cells is called the lattice. The unit cell is the smallest and simplest volume element that is completely representative of the whole crystal. If we know the exact contents of the unit cell, we can imagine the whole crystal as an efficiently packed array of many unit cells stacked beside and on top of each other, more or less like identical boxes in a warehouse. 

FIGURE 23.14 (a) Bipolar plates and a three-unit cell stack pressed between two metal collector plates,... 

Unit-cell stacks were developed specifically for concentrating solutions. Readers desiring information about unit-cell stacks are referred to Ref. 6. 

Yet another stack design utilizes unit cells. Unit-cell stacks were specifically developed for concentrating solutions. Each concentrating cell consists of one cation-exchange membrane and one anion-exchange membrane sealed at the edges to form an envelope with a spacer screen inside. The envelopes also have... 

In a sodium chloride crystal, the Na" and Cl ions are arranged in a giant lattice structure. The building brick of this structure is a unit cell is as shown in Fig 4.2. The larger spheres represent Cl ions, whereas the smaller spheres represent Na" ions. A crystal of sodium chloride consists of many billions of these unit cells stacked together in the lattice. 

The compound YBajCUjO, has been widely studied because it was the first superconductor discovered with a T above the boiling point of liquid nitrogen. The crystal stmcture of YBajCUjO, consists of three perovskite-like unit cells stacked one on top of the other (Figure 4.9a). If the ions are allocated the formal charges of Y ", Ba " and 0 , the Cu must take an average charge of 2.33, which can be considered to arise from the nominal presence of two Cu ions and one Cu ion per unit cell. 

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