Feb 3

Question 1

When you have Ewald’s sphere, when you rotate the lattice, how do you get concentric circles?

Answer 1

Diff points of lattice on the sphere, so you get a full circle concentric

Question 2

What are units of resolution in atomic scattering plot? What is on y axis? What happens with larger B factor/

Answer 2

Y axis is atomic scattering factor, then x axis is resolution (sin theta/lambda). With larger B (temperature) factor, the greater the fall-off, so the curve will reach zero on the y axis with a lower resolution than if the B factor was smaller

Question 3

What does a Wilson plot do/

Answer 3

It estimates the B-factor. The atomic scattering falls of due to the B factor and also just generally decreases as resolution increases. So you do ln(F^2/f^2) on y axis, which is structure factor squared divided by expected atomic scattering squared. Then on x axis have a square of the resolution so 4 (sin theta)^2 all divided by lambda^2, or you can simply have 1/d^2, where d is the interplanar spacing

Question 4

What are systematic absences/

Answer 4

They are when you get a pattern of seeing a point, then not in the same line. Always go off the center, in either the vertical or horizontal directions