Bragg's Law and lattice spacing problem

El Siglo

I'm currently starting work using XRD but there's something driving me mad, I came upon this website explaining how they worked out the lattice spacing for a specimen. However, every time I try and do it I keep getting a wrong answer for d in comparison to what the authors got. Would anyone here know what they managed to do?

Here's the example:

C. This is one of the X-ray peaks. It happens to be the one with the smallest angle which I measured as 23.04 degrees. Solving Bragg's Law (with n=1 and wavelength=1.54 ang) we find that 23.04 degrees 2-theta corresponds to a d-spacing of 3.86 angstrom.

Here's what I've done:

2d(sinθ)=λ

2d(sin 23.04)=1.54
2d(0.391)=1.54
0.782d=1.54
d=1.54/0.782
d=1.969

I'm not sure where I've gone wrong? Any help would be much appreciated!:D

Turtwig

El Siglo wrote: »

I'm currently starting work using XRD but there's something driving me mad, I came upon this website explaining how they worked out the lattice spacing for a specimen. However, every time I try and do it I keep getting a wrong answer for d in comparison to what the authors got. Would anyone here know what they managed to do?

Here's the example:


Here's what I've done:

2d(sinθ)=λ

2d(sin 23.04)=1.54
2d(0.391)=1.54
0.782d=1.54
d=1.54/0.782
d=1.969

I'm not sure where I've gone wrong? Any help would be much appreciated!:D

I think it's just their wording that's confusing you.

For practical reasons the diffractometer measures an angle twice that of the theta angle. Not surprisingly, we call the measured angle '2-theta'.

2θ = 23.04. θ = 11.52. Plug that in and you should get their values.:)

El Siglo

Malty_T wrote: »

El Siglo wrote: »

I'm currently starting work using XRD but there's something driving me mad, I came upon this website explaining how they worked out the lattice spacing for a specimen. However, every time I try and do it I keep getting a wrong answer for d in comparison to what the authors got. Would anyone here know what they managed to do?

Here's the example:


Here's what I've done:

2d(sinθ)=λ

2d(sin 23.04)=1.54
2d(0.391)=1.54
0.782d=1.54
d=1.54/0.782
d=1.969

I'm not sure where I've gone wrong? Any help would be much appreciated!:D

I think it's just their wording that's confusing you.

For practical reasons the diffractometer measures an angle twice that of the theta angle. Not surprisingly, we call the measured angle '2-theta'.

2θ = 23.04. θ = 11.52. Plug that in and you should get their values.:)

I just did it there and it came out correct, I feel like such an idiot! Thanks a million!