AC LEC 06-09

# AC LEC 06-09 - Lecture 6 - Crystallography; Atomic...

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Unformatted text preview: Lecture 6 - Crystallography; Atomic Positions, Directions, Planes Atomic positions Directions Planes Miller Indices Vector Algebra dot products cross products Hexagonal Crystals Miller-Bravais Indices CLOSE PACKED DISPLAY OF ORANGES How to Get These Lectures? Oak/2008.01.SPR.ENG.MSE.150.02 MAT SCI 1 LECTURES Space Lattice and Crystal Structure Observations A space lattice is a geometrical array of points in space Each point has identical surroundings When the “lattice points” are populated by atoms, we get a “CRYSTAL STRUCTURE” Atomic Positions in Unit Cells Convention 1 Positive X: Direction coming out of sheet Positive Y: Direction going to right edge of sheet Positive Z: Direction going to top edge of sheet Atom positions are located using unit distances along x, y and z axes Lets stick with CUBIC Lattice for the moment: a = b = c +Y +X +Z-Z-Y-X (0,0,0) (0,0,-1) (0,1,0) (-1,0,0) (1,0,0) (0,-1,0) (0,0,1) BCC STRUCTURE +Y +X +Z (0,0,0) (0,1,0) (1,0,0) (0,0,1) (0,1,1) (1,1,0) (1,1,1) (1,0,1) (1/2,1/2,1/2) a a a BCC ROTATION MOVIE FCC STRUCTURE (0,1,0) (1,0,0) (0,0,1) +Y +X +Z (0,1,1) (1,1,0) (1,0,1) a a a (1,1/2,1/2) (1/2,1/2,0) (1/2,1,1/2) (0,1/2,1/2) (1/2,0,1/2) (1/2,1/2,1) (0,0,0) (1,1,1) FCC ROTATION MOVIE Directions in Crystals (1) Resolve the direction along the coordinate axes Reduce to integers Enclose in SQUARE BRACKETS (no commas) EXAMPLES OA [110] OE [111] OB [100] OH [1 ½ 0] [210] +Y + X +Z O A C B F G D E 1/2H Directions in Crystals (2)...
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## This note was uploaded on 02/27/2009 for the course MSE 150 taught by Professor Wittig during the Spring '07 term at Vanderbilt.

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AC LEC 06-09 - Lecture 6 - Crystallography; Atomic...

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