RE: Parafocussing definition?

I just read through the rest of the discussion. He only thing to add is that I think the flat sample does play a role in the para part of the focusing. A real focusing experiment includes the light source entrance slit, “curved diffraction grating” (what we call our sample), and exit slits all

RE: software for correcting peak positions in capillary XRD data

Angel, Don't correct peak positions. Rather, use the appropriate parameter in your refinement software (in Fullprof, usually a combination of zero and sysin, but then again I usually have data from position sensitive detectors)(if your instrument was properly aligned, zero should refine to close

RE: Re : HT XRD calibration

Hi all, I've never used one of these Anton Paar furnaces, but with some of my instruments (externally heated, not Pt resistive foil heated) I could actually use the thermocouple as the sample mount. I also had an instrument that had a thermocouple in contact with the powder sample, which due

RE: Question about Fullprof

Dr. Alexandre (Alex) F. T. Yokochi Assistant Professor Department of Chemical Engineering Oregon State University Corvallis, OR 97331-2702 Voice: (541) 737-9357 Fax: (541) 737-4600 http://oregonstate.edu/~yokochia -Original Message- From: Yokochi, Alexandre [mailto:alexandre.yoko

Question about Fullprof

Hi everyone, Does anyone remember offhand how to turn on the output that includes calculated particle size when refining with a symmetry specific size model in Fullprof? I haven't looked at the program in a few years and am afraid I can't quite remember... Alex Y

RE: error in peak positions that is linear in theta

Hi all, Does the error maximize at 2-theta = 90 then decrease again? Back when I was an actual crystallographer and used an INEL system, this was observed when the capillary position was not coaxial with the detector (in fact, when it was behind the proper position). Alex Y

RE: source for Y2O3?

Kurt, Back when I was doing this I just purchased Y2O3 from a conventional chemical supplier and annealed it at high temperature (as high as you can easily get to, usually something like 1150C unless you have really fancy furnaces and crucibles) for a few days. Alex Y

RE: PDF refinement pros and cons

Pam and all, I too have been looking at materials using in house lab data. Using an Ag rotating anode (I actually used Ag-k beta for simplicity of the lack of peak splitting) and an MSC curved imaging plate, and very long exposures we got data we found quite useful. However, I stopped playing

RE: Analysis of data from instruments with theta-compensating slits

Patrick, The usual thing is to correct the data using a 1/(sin theta) correction. Notice that you'll have to create an ESD format file for GSAS and calculate what your ESDs (or SUs or whatever) in the corrected data is or you'll get funny statistics. The goal is I/sigma I stays constant - figure

RE: occupancy

Igor, Back when I used to do this a lot, the easiest way was to just start the occupancy of the two sites at 1 (e.g., 95% + 5%) then give one site a given variable and the second the opposite sign for the same variable (e.g., 20.5 and -20.5). I've been out of the XRD game for a few years, so

RE: Jorge González

Jorge, I purchased a Rigaku Rapid a few years ago (now superseded by the Spider, I believe) which I use extensively for single crystal, powder and thin film work. Unless you are extremely careful, the powder patterns can have somewhat broadened peaks which makes doing very high quality

RE: [sdpd] Material for calculation of IRF or IRP

SM, Having had INEL instruments, I would like to point out that you should carefully determine the angle between the primary beam and the sample when you make measurements on both standards and samples. This has a huge effect on line profiles. Peaks, especially very low angle ones, will have a

Re: Introductory presentation on PDFs

Hi Simon, Is this presentation part of the materials in your web site? If not, I would really like to look at it. Alex Y Dr. Alexandre (Alex) Yokochi Assistant Professor Department of Chemical Engineering Oregon State University Corvallis, OR 97331-2702 Phone: (541)-737-9357 Fax:

Re: Change format

Hi, One issue to consider is that many programs, when esd's of each datum are not given explicitly, estimate these as sqrt(I). Further, many programs weigh the data using these esd's. Therefore, since it is desired that esd/I remain a constant, if you do multiply your data by a constant, the

RE: Bond lengths calculation by Fullprof

Armel, Irini, and all, The option to do bond length calculations and BVS calculations, etc, is not explicitly given in the HTML fullprof manual. It is, however, described in the appendix included with the more recent releases of Fullprof (you know, the big ol pdf file called something

Negative displacement params in neutron refinement

Hi all, I have neutron data (constant wavelength) I have been working on and the displacement parameters of most atoms turn out to be negative along one axis (c in hexagonal setting). The material has relatively low absorption coefficient (mu*r approx .5), and (as expected) when a

Crystallographic data for Sucrose

Hi everyone, I have been interested on how well one of my diffractometers would do with organic samples (i.e., would it be useful for phase matching, or even SDPD) and am currently collecting a data set on Sucrose (table variety). I wonder if any of you that has access to the CSD

Toroidal atom displacement factors?

Hi everyone, I have some data where I suspect that an atom rather than sitting exactly on a special position is actually displaced off of it, and should essentially form a torus around it. I think I overheard that there is the possibility of using toroidal displacement factors in one of

RE: Re: Powder patterns from single crystal intensity data

Sean, Thanks, I'll give it a try. I am also to the point where I think writing a quick utility to do it would be trivial, so maybe I'll do it as soon as instrumentation quits breaking down (I've almost reached steady state!). Did you ever get an answer to your GSAS question?

Powder patterns from single crystal intensity data

Hi everyone, I am wondering whether there is an easy to use tool that will take a SHELX format intensity file and instrumental parameters (or even without these) and calculate a powder pattern out of that. I know that sometime ago someone asked exactly the question I am now

RE: none

Joe, You'll have fun and learn a lot of strange things playing with powders (I know I have). We have both a Siemens (Bruker) D5000 and two INEL systems. Both give excellent data, etc. The INEL systems, due to the parallel beam optics are way more sensitive to alignment.

RE: a few words about pdCIF

Howdy everyone, Concerning the data storage formats, Brian Toby wrote that (some time ago) am not sure that I would use CIF as my internal format, if I were to create a database, since it is not designed for searching, but I would certainly want the ability to