On Sun, 2013-09-01 at 22:28 +0200, James Holton wrote:
> ... but Bragg's genius was in simplifying all this to a little
> rule which tells you how much to turn the crystal to see a given spot.
> We sort of take this for granted now that we have automated
> diffractometers that do all the math
s answer. I had also been wondering about it. To
clearify it for myself, and maybe for a few other bulletin board readers, I
reworked the Bragg formula to:
sin(theta) = n*Lamda / 2*d
which means that if we take n=2, for the same sin(theta) d becomes twice as big
as well, which means that we des
On 22 August 2013 07:54, James Holton wrote:
> Well, yes, but that's something of an anachronism. Technically, a
> "Miller index" of h,k,l can only be a triplet of prime numbers (Miller, W.
> (1839). A treatise on crystallography. For J. & JJ Deighton.). This is
> because Miller was trying to
e unit cell dictates which sets of planes are able to constructively
>> diffract. However, there might not be anything physically present in the
>> crystal with that periodicity. In this case the corresponding reflection
>> will be weak or absent. This is the kind of informati
liche Nachricht-
Von: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] Im Auftrag von Edward
A. Berry
Gesendet: Freitag, 23. August 2013 01:01
An: CCP4BB@JISCMAIL.AC.UK
Betreff: Re: [ccp4bb] AW: [ccp4bb] Dependency of theta on n/d in Bragg's law
OK, I see my mistake. n has nothing to do with highe
com/s/gljckhw7ui6df6c/Booklet.pdf?m
Best,
D
-Original Message-
From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Dom
Bellini
Sent: 22 August 2013 23:38
To: ccp4bb
Subject: Re: [ccp4bb] AW: [ccp4bb] Dependency of theta on n/d in Bragg's law
Dear Community,
I have
. August 2013 01:01
An: CCP4BB@JISCMAIL.AC.UK
Betreff: Re: [ccp4bb] AW: [ccp4bb] Dependency of theta on n/d in Bragg's law
OK, I see my mistake. n has nothing to do with higher-order reflections or
planes at closer spacing than unit cell dimensions.
n >1 implies larger d, like the double
this will work.
>
> Sorry.
>
> D
>
>
> From: CCP4 bulletin board [CCP4BB@JISCMAIL.AC.UK] on behalf of Edward A.
> Berry [ber...@upstate.edu]
> Sent: 23 August 2013 00:01
> To: ccp4bb
> Subject: Re: [ccp4bb] AW: [ccp4bb] Dep
Subject: Re: [ccp4bb] AW: [ccp4bb] Dependency of theta on n/d in Bragg's law
OK, I see my mistake. n has nothing to do with higher-order
reflections or planes at closer spacing than unit cell dimensions.
n >1 implies larger d, like the double layer mentioned by the original
poster, and those tur
case.)
I never really saw it this way until I was forced to think about it by
this new thread � does this makes sense?
Gregg
-Original Message-
From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Edward A.
Berry
Sent: Thursday, August 22, 2013 2:16 PM
T
Re: [ccp4bb] AW: [ccp4bb] Dependency of theta on n/d in Bragg's law
On Thursday, August 22, 2013 02:19:11 pm Edward A. Berry wrote:
> One thing I find confusing is the different ways in which d is used.
> In deriving Braggs law, d is often presented as a unit cell dimension,
> and &quo
gt; > are really dealing with
> > 2*n*d*sin(theta)=n*lambda, and so the �n�s� cancel out. (Of course, I�m
> > dealing with the monochromatic case.)
> >
> > I never really saw it this way until I was forced to think about it
> > by this new thread � does this makes
n only.
(same would hold for 3'd order diffraction from 3 layers etc.)
> -Ursprüngliche Nachricht-
> Von: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] Im Auftrag von
> James Holton
> Gesendet: Donnerstag, 22. August 2013 08:55
> An: CCP4BB@JISCMAIL.AC.
August 22, 2013 2:16 PM
To: CCP4BB@JISCMAIL.AC.UK
Subject: Re: [ccp4bb] AW: [ccp4bb] Dependency of theta on n/d in Bragg's law
<mailto:herman.schreu...@sanofi.com> herman.schreu...@sanofi.com wrote:
> Dear James,
> thank you very much for this answer. I had also been wondering about it.
Dear Pietro,
The n in Bragg's Law is indeed most interesting for teachers and a most
delicate matter for those enquiring about it.
The diffraction grating equation, from which W L Bragg got the idea, a 'cheap
accolade' he said to have it named after him in his Scientific American
article, has
von James
Holton
Gesendet: Donnerstag, 22. August 2013 08:55
An: CCP4BB@JISCMAIL.AC.UK
Betreff: Re: [ccp4bb] Dependency of theta on n/d in Bragg's law
Well, yes, but that's something of an anachronism. Technically, a
"Miller index" of h,k,l can only be a triplet of prime numbers (
ccp4bb
Subject: [ccp4bb] Dependency of theta on n/d in Bragg's law
Dear all,
I am shocked by my own ignorance, and you feel free to do the same, but do
you agree with me that according to Bragg's Law a diffraction maximum at an
angle theta has contributions to its intensity from planes at
Auftrag von James
Holton
Gesendet: Donnerstag, 22. August 2013 08:55
An: CCP4BB@JISCMAIL.AC.UK
Betreff: Re: [ccp4bb] Dependency of theta on n/d in Bragg's law
Well, yes, but that's something of an anachronism. Technically, a
"Miller index" of h,k,l can only be a trip
Well, yes, but that's something of an anachronism. Technically, a
"Miller index" of h,k,l can only be a triplet of prime numbers (Miller,
W. (1839). A treatise on crystallography. For J. & JJ Deighton.). This
is because Miller was trying to explain crystal facets, and facets don't
have "har
Dear Pietro,
Ladd & Palmer book does explain it, just first example that springs to mind.
HTH
D
-Original Message-
From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Pietro
Roversi
Sent: 20 August 2013 15:37
To: ccp4bb
Subject: [ccp4bb] Dependency of theta on n/
-BEGIN PGP SIGNED MESSAGE-
Hash: SHA1
Dear Pietro,
You may take a textbook into account which deals with Laue
diffraction. If you search for the keyword "Laue" and the author
"Helliwell" at the IUCR journals, you will get a large number of hits,
indicating that this is by no means a 'triv
Dear all,
I am shocked by my own ignorance, and you feel free to do the same, but
do you agree with me that according to Bragg's Law
a diffraction maximum at an angle theta has contributions
to its intensity from planes at a spacing d for order 1,
planes of spacing 2*d for order n=2, etc. etc.?
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