CHM 111 Lecture Notes - Lecture 19: Bravais Lattice, Coordination Number, Crystal Structure
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Document Summary
Diffraction from a crystal: crystal lattice: the regular arrangements in a crystalline solid. X-ray diffraction analysis: unit cell: smallest unit that shows that pattern of arrangement. Unit cells are repeated over and over again. Unit cells are classified by their symmetry. Unit cells: coordination number: number of particles each particle comes in contact with. Higher coordination number = more interaction = stronger attractive forces holding the crystals together = higher packing efficiency: packing efficiency: percentage of particle volume in a unit cell. Cubic unit cells: angles are 90 degrees, length of all edges are equal, 3 types are simple cubic, body-centered cubic, and face-centered cubic, when there are spherical particles is within the cube. One half of each particle on a face. One fourth of each particle on an edge: simple cubic. Where r is the radius: edge of unit cell=2r: body-centered cubic. Edge of unit cell = (4/sqrt(3))r: face-centered cubic.
