materials and environment

Crystal structures (10p) a) Draw the SC, BCC and FCC crystal structures. Rank (in descending order) them by Atomic Packing Factor (APF). b) Explain how X-ray crystallography works and what information you get about the crystal structure when you use it to examine e.g. a metal. c) Calculate the theoretical density of chromium (Cr) using the following data: Theoretical density Pteort =VCNAnA the number of atoms in the unit cell, for nice =4; necc-2; n=6; A=atomic weight, can be found in tables or in the book. Also available in the lectures.. VC,BCC=a3,VC,FCC=a3,VC.HCP=6R2c3 NA-Avogadro's number Cr has R=0.1249nm and a==4R/3