Point atomgroup of atoms lattice parameters a b and c

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Unformatted text preview: 2013 IIT Gandhinagar 4 Crystal Lattice Crystal Lattice Crystal Lattice Lattice? Point – atom/group of atoms Lattice parameters? a, b, and, c and α, β, and γ Seven types of lattice structures 6 Three dimensional lattice P(uvw) = ua + vb + wc Simple coordinate geometry Choose an origin and move to the atom location 7 Lattice locations in BCC 8 Lattice locations in FCC 9 Crystallographic directions Vector – One end is origin [uvw] u projection on a axis v projection of b axis w projection on c axis u, v, and w are integers Bar above letters is used for negative direction projection 10 Crystallographic directions z b a/2 y x Line is drawn through the origin May be translated if parallelism is maintained Vector projection lengths on the three axes Reduce them to smallest integer values – divide or multiply by common factor x y z Projections a/2 b 0 In terms of a, b and c ½ 1 0 Indices 1 2 0 11 Crystallographic directions z 5 4 2 1 y 3 x 12 Finding Projection z y x 13 Finding Projection y x y x 14 Crystallographic directions z y [110] x 15 Crystallographic directions y x [101] z 16 Crystallographic directions x z [011] y 17 Family of directions Family of directions [100], [010], [001] and other three negative directions <uvw> - family of directions family Valid completely for cubic systems but limited for other systems 18 Summary Crystallographic points hkl Crystallographic directions [uvw] Family of directions <uvw> 19...
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