513.001 Molecular and Solid State Physics

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MIT 8.231 Physics of Solids, 1.1

A conventional (cubic) unit cell of gallium arsenide, GaAs, is shown below. Note the similarity to the diamond structure. The gallium atoms are indicated by shaded circles and the arsenic atoms by open circles.

a) How many atoms of each type are contained in a conventional unit cell?

b) To which space lattice type does this crystal lattice belong? In other words, what is the Bravais lattice?

c) Give a set of fundamental translation vectors (a, b, c) which can be used to define the primitive unit cell. Express your answer in cartesian coordiantes (x, y, z). How many atoms are there in the primitive cell?