Lecture 3 Flashcards
What is the coordination number for HCP? atoms/cell? a=? APF?
12
6
a=2r
APF= 0.74
What is the coordination number for CCP? atoms/cell? a=? APF?
12
4
2sqrt2 r
APF= 0.74
what is planar density
density of atoms on a particular crystal plane
how do you calculate planar density
= (# atoms on a plane* area occupied)/ area of the plane
do different crystallographic planes have different surface areas?
yes
Can properties change depending on the direction a plane is measured?
yes
what properties can change depending on the direction a plane is measured? why
hardness, resistivity, catalytic activity, etc.
depending on the planar density of the crystallographic plane
What is hardness anisotropy
the quality of exhibiting properties with different values when measured along axes in different directions
What do the (100) (110) (111) look like
what is the formula for planar density
PD = [(#atoms on a plane)(area occupied] / (area of the plane)
what is the planar density of the plane on the cube faces of ccp (100)
**base is a square
PD = (4atoms * pi*r^2)/(2sqrt(2)r)^2
what is the planar density of the (110) plane of a ccp
- use a and sqrt(2)a to calculate the area
** base is a rectangle
PD = (4pir^2)/[sqrt(2)a]
what is the planar density of the (111) ccp
**base is a triangle
What is the number for the planar density of the cubic face
0.785
what is the number for the planar density of the planes along the face diagonal (110)
0.555
What is the number for the planar density of the planes perpendicular to the body diagonal t of ccp (111)
0.907
how do you determine the ratio of c/a in the hcp structure
what is the c/a ratio for hcp
