MATS 3011 Lecture : Lecture 252014.pdf
Document Summary
Density calculation (relating lattice parameter and size of the atoms/ions) Point locations in a unit cell are identified as fraction of lattice constant. Can use density to calculate size of atom. Definition of crystal: all lattice pts are identical. To get to center of cube (1/2, 1/2, 1/2) For crystallogrphic directions: determine head & tail point & subtract (get direction, multiply/divide by common value (factor) to get the smallest integer, enclose whatever you get (indices) square brackets. Tail = (0,0,1) (defined origin where x,y, and z intersect Tail = (1,0,1/2) (0,0,1) - (1,0,1/2) = (1,0,-1/2) to get smallest integer, multiply by 2 ------> (2,0,-1) no comma, negative #s have bar on top. Since cubic system is symmetric, there are other equivalent directions or family of directions that are equivalent ex: (red = directions) [100] [010] [001] [1bar00]they are essentially the same since if you look from origin, you will see the same thing ----> symmetry.
