6 XRD (X-ray Diffraction) Flashcards

1
Q

what is XRD

A

-x-ray diffraction (powder diffraction)
-x-ray diffracted from crystal
- high E e (usually Mo or Cu), e ejected, e relaxes, x-ray emitted

  • get diffractogram
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the orbitals corresponding to emitted x rays

A
  • 2p 3/2 = Ka1
  • 2p 1/2= Ka2
  • 3p= Kb
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is bremsstrahlung radiation

A

-created non uniform background
- rad emitted when e decelerates as it encounters matter
-e slows as approach nuc, E releases as x-ray

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what do does K a or B and 1 or 2 stand for in Ka1

A

K = relaxes to 1s
a = from 2p
b= from 3p
1 or 2 = spin state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what are the sources of unwanted rad and how to rid?

A

-Kb and bremsstrahlung rad
- use filters 1 or 2 atomic numbers below
- or crystal oriented at specific angle

Cu for Kb and Ni for Brem

  • Ka1 and Ka2 appear monochromatic, can’t get rid of it
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is Braggs law?

A

diffracted rays either constructive or destructive
(constructive if 1 wavelength apart)

sin^2= lambda^2/(4a^2)(h^2+k^2+l^2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

can you use peak intensity to do quantitative stiff?

A

no

can if have more info

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

how to prepare sample for XRD

A
  • ground to powder get small crystals with all possible orientation

get measure that is 2theta (important part)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

pros XRD

A
  • fast, easy, cheap
  • large library known samples
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what does amorphous look like?

A

large hump instead sharp peaks

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is the Scherrer analysis

A

-estimate size nano crystal (less100nm and spherical)
- particles smaller fewer planes produce constative interference, get broader peaks

above 200nm other broadening effects and can’t analyze

  • complementary tech, only sees small part
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Systematic absences

A

-planes that reflect

  • BCC: addition miller indices multiple of 2
  • FCC: miller indices either all odd or even
How well did you know this?
1
Not at all
2
3
4
5
Perfectly