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Unformatted text preview: ENSC 3313, Spring 2004 Quiz 2- ANSWERS Name_________________________ Answer ONLY 4 of the 6 questions, show all work, 1point each 1. We know that copper has the FCC crystal structure with an atomic radius of 0.128 nm and that it is very ductile. Calculate the planar density of copper atoms on the (111) plane in units of 1/nm 2 . The number of atoms per unit cell on the (111) plane is 2 (i.e., count 1/6 of the 3 corner atoms and 1/2 of the 3 face atoms). Now we calculate the area of this plane. 2 ) 111 ( 3 4 ) 12 )( 4 ( 2 1 R R R A = = 2 2 62 . 17 ) 128 . ( 3 4 2 = = nm PD 2. Enumerate the relationship between side lengths and the number of four fold symmetry axes for cubic, tetragonal, and orthorhombic unit cells. Which unit cell has a three fold axis of symmetry? Cubic has 3 four fold axes Tetragonal has 1 four fold axis Orthorhombic has 0 four fold axes The cubic unit cell has three fold symmetry axes along the body diagonals 3. SiC is a hard ceramic used as an abrasive with highly covalent bonding and crystal structure similar to...
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