Re: Explaining for broadening of peaks due to a shift of theta in theta-two theta scanning?

Besides Joerg's suggestion of mis-cut substrates (which may be too expensive for use for thin film growth experiments) you could use Si wafers cut to (100). The first allowed peak in that direction is (400), which is at about 70 degrees 2theta for Cu K-alpha. That will still reflect any brems

Fw: Anisotropic peak broadening with TOPAS

In response to the question posted this morning by Frank Girgsdies: Here is a little snatch of topas code for anisotropic broadening in orthorhombic system. (The fitted parameters come from a particular refinement I took this from; the factor of 10^4 is empirically chosen to get parameter valu

Re: problem with Si powder pattern

The space group of silicon is Fd-3m (usually written with bar over the three). There are two settings of that space group. (This situation arises because the point of highest symmetry does not coincide with the point of fewest equivalent Wyckoff positions.) Have a look at the drawings in the

Re: help

Can you be more specific? ^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~ Peter W. Stephens Professor, Department of Physics and Astronomy Stony Brook University Stony Brook, NY 11794-3800 fax 631-632-8176

Re: More Caglioti U V W parameters

In my opinion, the short answer (regarding use of Caglioti parameters) is that their use is historic and somewhat convenient, but their usual application is based on no theory whatsoever, and they can be quite troublesome to apply. They came from a paper (Nuc. Instrum. & Methods, 1958) on the r

Powder Diffraction at NSLS-II

Friends and colleagues, You may be aware that plans are afoot to build a new synchrotron light source, dubbed NSLS-II, at Brookhaven Lab. This will be a medium energy (3 GeV) storage ring of extremely high brightness, proposed to start operations in 2013. I am writing to ask you to attend the

OOPS.

Sorry about that. ^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~ Peter W. Stephens Professor, Department of Physics and Astronomy Stony Brook University Stony Brook, NY 11794-3800 fax 631-632-8176

Re: Powder Diffraction In Q-Space

Simon, You left a couple of jackets at my house - they're on their way back to you. Did you see anything interesting with the realtor? Do let us know if you'll be coming back for another visit with your wife. Best, Peter ^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~ Peter W. Stephens Prof

Re: Strange peaks from grainy Si

I'll mail you some fine Si powder if you send me your address. My best guess is that you have a relatively big lump of Si in your sample that happens to be lined up to make a bright spot from the bremstrahlung part of the spectrum. It happens to meet some Si Bragg reflection condition for some

Re: Synchrotron Powder Diffraction Course

Sorry to blast you all with that correspondence.  Once again, we are reminded that the "reply" key is a dangerous part of email! -Peter

Re: Synchrotron Powder Diffraction Course

Thanks, nice to hear from you.   Actually, Silvia Cuffini has invited me as an instructor in a crystallography workshop next November; I'm not completely clear on the exact venue or schedule. Best, Peter ~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~^~ Peter W. Stephens, Professor Department of Physics

Synchrotron Powder Diffraction Course

Dear Colleagues, I am writing to call your attention to a three-day course, "High Resolution Powder Diffraction Data Collection and Analysis" to be held at the National Synchrotron Light Source, January 25-27, 2005.  This will be a blend of instruction, practical experience at synchrotron beamlin

RE: Anisotropic line broadening in cubic material

Jens, Your effect might be more related to strain than size broadening. You would have to check widths at various diffraction orders in a given direction (i.e., 111, 222, 333, etc., vs 200, 400, 600, etc. for an fcc material). If the widths increase roughly in proportion to diffraction orde

Re: space group of NaxCoO2

I just recalled a more directly relevant paper for your question: M.L. Foo et al., Phys. Rev. Letters 92, 247001 (2004), published about six weeks ago.  That paper is much more about electronic properties through the phase diagram as a function of x, but it will help get you oriented, and has some

Re: space group of NaxCoO2

You should start with the paper by J.D. Jorgensen et al., Phys. Rev. B 68, 214517 (2003).  I don't have that paper in front of me, and so I don't know if it completely addresses the space group issue of both phases, but it will get you in touch with the recent literature. ~^~^~^~^~^~^~^~^~^~^~^~^

Re: indexing problem

Topas software is very good at solving such short axis problems.  The advantage is that it will look at all of the peaks you feed it, instead of using just the first twenty or so to generate candidate solutions (the way that ITO and TREOR work). If you don't have access to Topas, I suggest the fo