Re: PO corrections in trigonal space groups?
Ta a lot for that Reinhard.
I'll have a read of the paper and see what I can do. I need to read more on
spherical harmonics as well, as they seem a little like magic to me at the
moment.
I agree that the best way is to avoid PO in the first place, but (at least
in this instance) it wasn't in my control.
Thanks
Matthew
On Wednesday, 26 March 2014, Reinhard Kleeberg <
kleeb...@mineral.tu-freiberg.de> wrote:
> Dear Matthew,
> in my knowledge, for calcite the {104} in the usual cell choice for
> hexagonal axes is equivalent to {10-11} in rhombohedral axes setting.
> Morphologically, this shape is called by mineralogists the "main
> rhombohedra" and the six faces belonging to {104} are indeed the directions
> of the perfect cleavage. Thus, the shape of calcite particles
> crushed/milled from bigger crystals are nearly perfect rhombohedra (btw a
> typical exercise used in undergraduate mineralogy classes for demonstrating
> "cleavage").
> In common powder sample preparation, you can expect preferred orientation
> of these planes parallel to the sample surface. For Bragg-Brentano geometry
> (rotational symmetric, observation direction perpendicular to the sample
> surface), you need any function fulfilling the symmetry of the Laue class
> for the description of the relative polar-axis density of the hkl oriented
> parallel to the sample surface. This is realized by symmetrized spherical
> harmonics as introduced by Järvinen et al. (1970), Popa (1992), Järvinen
> (1993, 1998). This and similar approaches are included in many Rietveld
> programs, e.g. GSAS, TOPAS, BGMN, MAUD, DDM (?)...
>
> Back to calcite: You can see an example of a practically working
> correction function in fig. 1c of
>
> Bergmann, J., Monecke, T., Kleeberg, R. (2001) Alternative algorithm for
> the correction of preferred orientation in Rietveld analysis. J. Appl.
> Cryst. 34, 16-19.
> This function has maxima in the direction of the {104} normal vectors. As
> Leonid wrote, the description of such a rhombohedral symmetry is not
> possible by any uniaxial function like March-Dollase related to one special
> hkl. So there is no way around to choose a more complicated model than the
> March-Dollase.
>
> However, keep in mind that all these models like spherical harmonics have
> no real physical meaning and are limited in their application. They can
> effectively describe the PO only for rotational symmetry of your
> diffraction experiment, only up to a certain (weak) degree of PO, and only
> if there is a homogeneous PO in your powder sample. So the application of
> any PO correction models in Rietveld analysis is a potential source of
> errors and just the second-best solution. The best is always an optimized
> preparation for a randomly oriented powder mount.
>
> Reinhard
>
> Am 26/03/2014 05:46, schrieb Leonid Solovyov:
>
> Dear Mathew,
>
> The 104 plane in calcite corresponds to the most intense reflection that is
> related, in turn, to the best "spacing" or "separation" between atomic
> "layers" along which the cleavage may occur. This is not a strict rule, of
> course, as real cleavage planes may be different depending on specific
> interatomic interactions in the crystal and other aspects, but it works in
> many cases.
> Note also, that the 104 plane in the hexagonal setting has several
> symmetry-equivalents, while most Rietveld programs normally generate only one
> equivalent hkl for each diffraction peak, which makes the uniaxial
> March-Dollase PO correction invalid for such peculiar directions. This
> problem is resolved in DDM, where I included a special expanded-hkl option to
> generate all equivalent hkl's for every peak. About other programs I'm not
> sure.
>
> Best regards,
> Leonid
> ***
> Leonid A. Solovyov
> Institute of Chemistry and Chemical Technology
> 660036, Akademgorodok 50/24, Krasnoyarsk, Russiasolovyovleonid
> <http://sites.google.com/site/solovyovleonid>
> *******************
>
>
>
> From: Matthew Rowles
>
> To: "Sitepu, Husinsyah"
>
> Cc: "daniel.chateig...@ensicaen.fr"
>
>
> ;
> "rietveld_l@ill.fr"
>
> Sent: Wednesday, March 26, 2014 8:16 AM
> Subject: Re: PO corrections in trigonal space groups?
>
>
>
> Thanks for your replies.
>
> Husin, is there any justification for the use of the 104 direction in
> calcite, other than this is the direction that works? I'm all for doing it if
> it works, but I'd like a little theoretical backup.
>
> Thanks Daniel. I'll
Re: PO corrections in trigonal space groups?
Dear Matthew,
in my knowledge, for calcite the {104} in the usual cell choice for
hexagonal axes is equivalent to {10-11} in rhombohedral axes setting.
Morphologically, this shape is called by mineralogists the "main
rhombohedra" and the six faces belonging to {104} are indeed the
directions of the perfect cleavage. Thus, the shape of calcite particles
crushed/milled from bigger crystals are nearly perfect rhombohedra (btw
a typical exercise used in undergraduate mineralogy classes for
demonstrating "cleavage").
In common powder sample preparation, you can expect preferred
orientation of these planes parallel to the sample surface. For
Bragg-Brentano geometry (rotational symmetric, observation direction
perpendicular to the sample surface), you need any function fulfilling
the symmetry of the Laue class for the description of the relative
polar-axis density of the hkl oriented parallel to the sample surface.
This is realized by symmetrized spherical harmonics as introduced by
Järvinen et al. (1970), Popa (1992), Järvinen (1993, 1998). This and
similar approaches are included in many Rietveld programs, e.g. GSAS,
TOPAS, BGMN, MAUD, DDM (?)...
Back to calcite: You can see an example of a practically working
correction function in fig. 1c of
Bergmann, J., Monecke, T., Kleeberg, R. (2001) Alternative algorithm for
the correction of preferred orientation in Rietveld analysis. J. Appl.
Cryst. 34, 16-19.
This function has maxima in the direction of the {104} normal vectors.
As Leonid wrote, the description of such a rhombohedral symmetry is not
possible by any uniaxial function like March-Dollase related to one
special hkl. So there is no way around to choose a more complicated
model than the March-Dollase.
However, keep in mind that all these models like spherical harmonics
have no real physical meaning and are limited in their application. They
can effectively describe the PO only for rotational symmetry of your
diffraction experiment, only up to a certain (weak) degree of PO, and
only if there is a homogeneous PO in your powder sample. So the
application of any PO correction models in Rietveld analysis is a
potential source of errors and just the second-best solution. The best
is always an optimized preparation for a randomly oriented powder mount.
Reinhard
Am 26/03/2014 05:46, schrieb Leonid Solovyov:
Dear Mathew,
The 104 plane in calcite corresponds to the most intense reflection that is related, in turn, to the best
"spacing" or "separation" between atomic "layers" along which the cleavage may
occur. This is not a strict rule, of course, as real cleavage planes may be different depending on specific
interatomic interactions in the crystal and other aspects, but it works in many cases.
Note also, that the 104 plane in the hexagonal setting has several
symmetry-equivalents, while most Rietveld programs normally generate only one
equivalent hkl for each diffraction peak, which makes the uniaxial
March-Dollase PO correction invalid for such peculiar directions. This problem
is resolved in DDM, where I included a special expanded-hkl option to generate
all equivalent hkl's for every peak. About other programs I'm not sure.
Best regards,
Leonid
***
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660036, Akademgorodok 50/24, Krasnoyarsk, Russia
http://sites.google.com/site/solovyovleonid
***
From: Matthew Rowles
To: "Sitepu, Husinsyah"
Cc: "daniel.chateig...@ensicaen.fr" ;
"rietveld_l@ill.fr"
Sent: Wednesday, March 26, 2014 8:16 AM
Subject: Re: PO corrections in trigonal space groups?
Thanks for your replies.
Husin, is there any justification for the use of the 104 direction in calcite,
other than this is the direction that works? I'm all for doing it if it works,
but I'd like a little theoretical backup.
Thanks Daniel. I'll put something together for a look-see. What corrections are
being used in Maud? Are there any papers on them?
THanks
Matthew
--
TU Bergakademie Freiberg
Dr. R. Kleeberg
Mineralogisches Labor
Brennhausgasse 14
D-09596 Freiberg
Tel.++49 (0) 3731-39-3244
Fax. ++49 (0) 3731-39-3129
++
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Re: PO corrections in trigonal space groups?
Dear Mathew, The 104 plane in calcite corresponds to the most intense reflection that is related, in turn, to the best "spacing" or "separation" between atomic "layers" along which the cleavage may occur. This is not a strict rule, of course, as real cleavage planes may be different depending on specific interatomic interactions in the crystal and other aspects, but it works in many cases. Note also, that the 104 plane in the hexagonal setting has several symmetry-equivalents, while most Rietveld programs normally generate only one equivalent hkl for each diffraction peak, which makes the uniaxial March-Dollase PO correction invalid for such peculiar directions. This problem is resolved in DDM, where I included a special expanded-hkl option to generate all equivalent hkl's for every peak. About other programs I'm not sure. Best regards, Leonid *** Leonid A. Solovyov Institute of Chemistry and Chemical Technology 660036, Akademgorodok 50/24, Krasnoyarsk, Russia http://sites.google.com/site/solovyovleonid *** From: Matthew Rowles To: "Sitepu, Husinsyah" Cc: "daniel.chateig...@ensicaen.fr" ; "rietveld_l@ill.fr" Sent: Wednesday, March 26, 2014 8:16 AM Subject: Re: PO corrections in trigonal space groups? Thanks for your replies. Husin, is there any justification for the use of the 104 direction in calcite, other than this is the direction that works? I'm all for doing it if it works, but I'd like a little theoretical backup. Thanks Daniel. I'll put something together for a look-see. What corrections are being used in Maud? Are there any papers on them? THanks Matthew ++ Please do NOT attach files to the whole list Send commands to eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++
Re: PO corrections in trigonal space groups?
Thanks for your replies.
Husin, is there any justification for the use of the 104 direction in
calcite, other than this is the direction that works? I'm all for doing it
if it works, but I'd like a little theoretical backup.
Thanks Daniel. I'll put something together for a look-see. What corrections
are being used in Maud? Are there any papers on them?
THanks
Matthew
On 25 March 2014 22:32, Sitepu, Husinsyah wrote:
> Dear Matthew,
>
>
>
> Following to Professor Daniel Chateigner 's email, I would like to
> highlight briefly that the preferred orientation (PO) directions for
> calcite (CaCO3) that we used during the refinement using GSAS were
>
> · <104> for X-ray diffraction data, and
>
> · <001> for neutron diffraction data.
>
> Please see the Curtin Library
> link<http://espace.library.curtin.edu.au/R?func=dbin-jump-full&object_id=10543>or
> IUCr Journal of Applied Crystallography, Volume
> 35, Part 2 (April
> 2002)<http://journals.iucr.org/j/issues/2002/02/00/issconts.html> and
> Volume 38, Part 1 (February
> 2005)<http://journals.iucr.org/j/issues/2002/02/00/issconts.html>for the
> details.
>
>
>
> With best wishes,
>
>
>
> Husin
>
> ___
>
> *Husin Sitepu, PhD*
>
> SAUDI ARAMCO
>
> RESEARCH & DEVELOPMENT CENTER
>
> Dhahran, PO Box 31311, KSA
>
> Phone: *+966* *876-3050*
>
> Email: sitep...@aramco.com
>
>
> http://scholar.google.com/citations?hl=en&user=cUTV8HkJ&view_op=list_works&pagesize=100
>
>
> ___
>
>
>
>
>
> -----Original Message-
> From: rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] On
> Behalf Of daniel Chateigner
> Sent: Tuesday, March 25, 2014 2:10 PM
> To: rietveld_l@ill.fr
> Subject: Re: PO corrections in trigonal space groups?
>
>
>
> Hi Matthew,
>
>
>
> You would perhaps prefer physically meaningfull PO correction using
> standard functions, at disposal in Maud. If you can give me an ascii double
> column of your data I'll give it a trial.
>
>
>
> daniel
>
>
>
> Le 25/03/2014 11:43, Matthew Rowles a écrit :
>
> > Hi all
>
> >
>
> > I have a sample containing a fraction of calcite. My research tells me
>
> > that calcite cleaves on {10-11}.
>
> >
>
> > How can I express this as an hkl for the March-Dollase PO correction?
>
> >
>
> > By inspection, {104} is the direction that orients. Is that correct?
>
> > How can I derive that?
>
> >
>
> >
>
> > Thanks
>
> >
>
> >
>
> > Matthew Rowles
>
>
>
> --
>
> http://www.ecole.ensicaen.fr/~chateign/danielc/
>
>
>
> Address:
>
> IUT-Caen Université de Caen Basse-Normandie and CRISMAT-ENSICAEN
>
> 6 Bd. M. Juin, 14050 Caen
>
>
>
> The Crystallography Open Database: www.crystallography.net The Materials
> Property Open Database: http://www.materialproperties.org/
>
> Combined Analysis using rays:
> http://iste.co.uk/index.php?f=x&ACTION=View&id=359
>
>
>
> --
>
> The contents of this email, including all related responses, files and
> attachments transmitted with it (collectively referred to as "this Email"),
> are intended solely for the use of the individual/entity to whom/which they
> are addressed, and may contain confidential and/or legally privileged
> information. This Email may not be disclosed or forwarded to anyone else
> without authorization from the originator of this Email. If you have
> received this Email in error, please notify the sender immediately and
> delete all copies from your system. Please note that the views or opinions
> presented in this Email are those of the author and may not necessarily
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> ++
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> ++
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RE: PO corrections in trigonal space groups?
Dear Matthew,
Following to Professor Daniel Chateigner 's email, I would like to highlight
briefly that the preferred orientation (PO) directions for calcite (CaCO3) that
we used during the refinement using GSAS were
· <104> for X-ray diffraction data, and
· <001> for neutron diffraction data.
Please see the Curtin Library
link<http://espace.library.curtin.edu.au/R?func=dbin-jump-full&object_id=10543>
or IUCr Journal of Applied Crystallography, Volume 35, Part 2 (April
2002)<http://journals.iucr.org/j/issues/2002/02/00/issconts.html> and Volume
38, Part 1 (February
2005)<http://journals.iucr.org/j/issues/2002/02/00/issconts.html> for the
details.
With best wishes,
Husin
___
Husin Sitepu, PhD
SAUDI ARAMCO
RESEARCH & DEVELOPMENT CENTER
Dhahran, PO Box 31311, KSA
Phone: +966 876-3050
Email: sitep...@aramco.com<mailto:sitep...@aramco.com>
http://scholar.google.com/citations?hl=en&user=cUTV8HkJ&view_op=list_works&pagesize=100
___
-Original Message-
From: rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] On Behalf Of
daniel Chateigner
Sent: Tuesday, March 25, 2014 2:10 PM
To: rietveld_l@ill.fr
Subject: Re: PO corrections in trigonal space groups?
Hi Matthew,
You would perhaps prefer physically meaningfull PO correction using standard
functions, at disposal in Maud. If you can give me an ascii double column of
your data I'll give it a trial.
daniel
Le 25/03/2014 11:43, Matthew Rowles a écrit :
> Hi all
>
> I have a sample containing a fraction of calcite. My research tells me
> that calcite cleaves on {10-11}.
>
> How can I express this as an hkl for the March-Dollase PO correction?
>
> By inspection, {104} is the direction that orients. Is that correct?
> How can I derive that?
>
>
> Thanks
>
>
> Matthew Rowles
--
http://www.ecole.ensicaen.fr/~chateign/danielc/
Address:
IUT-Caen Université de Caen Basse-Normandie and CRISMAT-ENSICAEN
6 Bd. M. Juin, 14050 Caen
The Crystallography Open Database:
www.crystallography.net<http://www.crystallography.net> The Materials Property
Open Database: http://www.materialproperties.org/
Combined Analysis using rays: http://iste.co.uk/index.php?f=x&ACTION=View&id=359
The contents of this email, including all related responses, files and
attachments transmitted with it (collectively referred to as “this Email”), are
intended solely for the use of the individual/entity to whom/which they are
addressed, and may contain confidential and/or legally privileged information.
This Email may not be disclosed or forwarded to anyone else without
authorization from the originator of this Email. If you have received this
Email in error, please notify the sender immediately and delete all copies from
your system. Please note that the views or opinions presented in this Email are
those of the author and may not necessarily represent those of Saudi Aramco.
The recipient should check this Email and any attachments for the presence of
any viruses. Saudi Aramco accepts no liability for any damage caused by any
virus/error transmitted by this Email.
++
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Re: PO corrections in trigonal space groups?
Hi Matthew,
You would perhaps prefer physically meaningfull PO correction using
standard functions, at disposal in Maud. If you can give me an ascii
double column of your data I'll give it a trial.
daniel
Le 25/03/2014 11:43, Matthew Rowles a écrit :
Hi all
I have a sample containing a fraction of calcite. My research tells me
that calcite cleaves on {10-11}.
How can I express this as an hkl for the March-Dollase PO correction?
By inspection, {104} is the direction that orients. Is that correct?
How can I derive that?
Thanks
Matthew Rowles
--
http://www.ecole.ensicaen.fr/~chateign/danielc/
Address:
IUT-Caen Université de Caen Basse-Normandie and
CRISMAT-ENSICAEN
6 Bd. M. Juin, 14050 Caen
The Crystallography Open Database: www.crystallography.net
The Materials Property Open Database: http://www.materialproperties.org/
Combined Analysis using rays: http://iste.co.uk/index.php?f=x&ACTION=View&id=359
++
Please do NOT attach files to the whole list
Send commands to eg: HELP as the subject with no body text
The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/
++
PO corrections in trigonal space groups?
Hi all
I have a sample containing a fraction of calcite. My research tells me that
calcite cleaves on {10-11}.
How can I express this as an hkl for the March-Dollase PO correction?
By inspection, {104} is the direction that orients. Is that correct? How
can I derive that?
Thanks
Matthew Rowles
++
Please do NOT attach files to the whole list
Send commands to eg: HELP as the subject with no body text
The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/
++
