ZnS is also a polymorphic (same composition, different structures) compound, with two known structures. Sphalerite (also...

   

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ZnS is also a polymorphic (same composition, different structures) compound, with two known structures. Sphalerite (also called zincblende) is cubic (space group 216: F43m, with a = 5.41A) and Zn at (0,0,0), S at (0.25, 0.25, 0.25) and all symmetry related positions). Wurtzite has the space group P63mc with a = 3.81Å, c = 6.23A, with Zn at (2/3, 1/3, 0) and S at (2/3, 1/3, 3/8). These two structures are adopted by many semiconducting materials. The differences in the structures profoundly impact the properties. a. Draw a unit cell of sphalerite. Describe the relation between this and the diamond structure. b. Draw several unit cells of wurtzite, showing the bonds between the atoms. c. Contrast the crystal structures of zincblende and wurtzite, comparing coordinations of atoms, bond lengths, and assembly of the polyhedra into the crystal structure. ZnS is also a polymorphic (same composition, different structures) compound, with two known structures. Sphalerite (also called zincblende) is cubic (space group 216: F43m, with a = 5.41A) and Zn at (0,0,0), S at (0.25, 0.25, 0.25) and all symmetry related positions). Wurtzite has the space group P63mc with a = 3.81Å, c = 6.23A, with Zn at (2/3, 1/3, 0) and S at (2/3, 1/3, 3/8). These two structures are adopted by many semiconducting materials. The differences in the structures profoundly impact the properties. a. Draw a unit cell of sphalerite. Describe the relation between this and the diamond structure. b. Draw several unit cells of wurtzite, showing the bonds between the atoms. c. Contrast the crystal structures of zincblende and wurtzite, comparing coordinations of atoms, bond lengths, and assembly of the polyhedra into the crystal structure.