Question

(5 pts.) Draw a BCC unit cell with labelled axes. List out the unique close-packed directions. How many are there?

Answer 1

N CO,0,1) 110,0,0) 10,1,0) 701,0,0) In the Bcc unit cell the atoms are situated in the 8- corners eight atoms and in the body one atom. So, effective number of atoms *8 + 1*1 = 2 [: Corner Shearing = 1/8 and body shearring 1] 2 7 Length of oA = 3a 1 [ia-latice - Parameter] No. of atoms situated on O4 = 2 , on Bcc ato unit cell the unique closed packed direction is [111]. as in which direction the linear direction is maxium is called the closed packed direction. so [111] direction is the most closed packed direction and it is situated along the body diagonal. Linear densit g [111] direction is LDC) - no. of atoms situated in that direction length of the direction Ii length of the body L igonal 23a, whore aselttice parameter 20 escused packed direction de coger entrenare presentes 2