Register to reply

Bragg peaks and bases

by Ichimaru
Tags: bases, bragg, peaks
Share this thread:
Apr16-14, 04:02 AM
P: 9
Question statement: We are given that Ca and CaF2 are both Ca face-centred cubic lattices, and that in the case of CaF2 there is a basis of F ions at +/-(1/4, 1/4, 1/4). Then explain qualitatively how the ratio of the (2 0 0) and (4 0 0) Bragg peak intensities in the X-ray diffraction patterns of Ca and CaF2 would differ.

Attempt at Solution: The main difference I can think of is that the planes defined by (4 0 0) would go through the F ions as well as Ca ions in the CaF2 lattice whereas the (2 0 0) planes would not intersect any F ions. In contrast the (4 0 0) planes and (2 0 0) planes in Ca would intersect the same atoms, and there would be empty planes in the (4 0 0) case.

However when I try to compute the ratios I get that they are the same, as the extra structure factor in the case of CaF2 just cancels itself out when comparing the (4 0 0) and (2 0 0) structure factors.

Any input would be appreciated.
Phys.Org News Partner Science news on
Wearable 4MM jetpack tested on speed, agility for runners (w/ Video)
How did evolution optimize circadian clocks?
Corn spots: Study finds important genes in defense response
Apr16-14, 11:54 PM
P: 1,985
Are you sure you put all the terms in the structure factor formula? How many fluorine atoms have you considered in the conventional cell?

Register to reply

Related Discussions
Coefficient of linear expansion / Bragg peaks Advanced Physics Homework 1
Bragg peaks Atomic, Solid State, Comp. Physics 10
Ratio of logarithms in various bases to other bases General Math 6
Unexpected peaks! Atomic, Solid State, Comp. Physics 4
Distance between peaks? Astronomy & Astrophysics 7