Request of Atomic coordinates of CuAlO2

Dear All, can anyone of you send me the CIF or the coordinate of CuAlO2? It has the following lattice parameters: a=2.85, c =16.94 alpha = beta = 90, gamma = 120, V = 119.7. Space group R-3m Hexagonal (Rhomhedral, No 166). many thanks in advance. stephen

change of my email

Dear Rietvelders, Please use my new email a/c chui...@hkucc.hku.hk. The current email will be not removed soon. best regards stephen

non-bond distances with esd in GSAS/EXGUI

Dear all, does anyone of you know how to find/specify the non-bonded distances with esd in the GSAS/EXGUI? I checked the output file from DISAGL, but there are only distances between "chemical bonds". can i specify a given atom pair for distance calculation? many thanks in advance best reg

Re: LP factor in the Rietveld refinement

Dear Ross, How about the LP factor/monochromator angle if using Gobel mirror in my D8 system? Thanks! stephen - Message from ucca...@ucl.ac.uk - Date: Thu, 23 Jul 2009 09:52:55 +0100 From: Ross H Colman Reply-To: Ross H Colman Subject: Re: LP factor in the Rietveld r

Suggestion about software(s) for size profile-broadening calculation

Dear all experts in XRD, As stated in the header, does anyone know if there is some software(s) available for estimation of average crystal grain size using the peak breath of XRD data? I just want to know some rough values so as to compare my samples prepared at different conditions. Many

Program for checking symmetry

Dear all, Recently, I have refined the structure using powder data. In each asymmetric unit of Pmc21, there are two chemically similar but crystallographically different complexes. The center of these two complexes is rougly around 0,0,0.75. Therefore, the true space group may not be Pmc2

Comment on Ball Miller

Dear all rietvelders, Do anyone of you use the ball miller for PXRD sample preparation? Since I am going to buy one such system. Any comment is highly appreciated. many thanks in advance stephen

Request of atomic coordinates of Cu2Se

Dear all rietvalders, Can anyone of you kindly send me the atomic coordinates? 1) Cu2Se cubic form (PDF-2 71-0044 a = 5.7650, Fm-3m) 2) Cu2Se cubic form (PDF-2 76-0136 a = 5.84, F23) 3) Cu2Se tetragonal form (PDF-2 53-0523 a = 11.510, c = 11.740, P4/mmm or P42/n) many thanks stephen

Change of email address

Dear Sir/Madam, can you please to replace my current email address ([EMAIL PROTECTED]) with the new one: [EMAIL PROTECTED] because the former will be removed. many thanks stephen

Request of atomic coordinate of Berzelianite Cu2Se

Dear all rietvelders, would anyone of you kindly provide me the atomic coordinates of Cu2Se (Berzelianite, Powder Diffraction File PDF-2 071-0044, Cubic Fm3m)? Great appreciate! cheers stephen

peak position of W L-alpha for Cu X-ray tube

Dear All rietvelders, can you remind me what the peak position of the tungsten L-alpha for the Cu X-ray tube? I am curious to estimate the lifetime of our Xray tube used for 2 year. many thanks stephen

Re: Tables of atomic, covalent and vdW radius of elements

Dear all, thank a lot. stephen Quoting Jacco van de Streek <[EMAIL PROTECTED]>: > [EMAIL PROTECTED] wrote: > > can anyone of you know something about this issue? > > Thank you for your help. > > Dear Stephen, > > tables with values for covalent and vdW radii for organic and > organometallic

Tables of atomic, covalent and vdW radius of elements

Dear all, can anyone of you know something about this issue? Thank you for your help. regards stephen

Re: Space group of Si standard in XRD

Dear all, Thank you very much for your information. I think the one I am using is Si[111]. It was used for checking the linearity of the diffractometer. I just curious to see some rietveld refinement can be practised myself. I got R-factor (R(F2)) ca. 15% and the simulated PXRD from Si structure

Space group of Si standard in XRD

Dear colleagues can anyone remind me the space group and lattice constants of the Si standard (flat plate) used in the Philips APD B-B diffractometer? Since I will like to do some comparison studies using GSAS. Many thanks, regards stephen

Optimization of intermolecular void space

Dear all, Can anyone know how to optimize the intermolecular contacts of say, a rigid organic molecule such as naphthalene etc if we know there is no occluded solvent molecule but the cell volume/density is too far from typical range? In case of any ambiguity, please feel free to discuss. many t

Enquiry of XRD standard materials

Dear Rietvelders, Does anyone can provide the sources for purchasing XRD standards materials, such as CeO2 and Y2O3? I need few grams of these for calibration of our XRD. Thank in advance. regards stephen

GSAS - R(free) sampling factor and seed

Dear Rietvelders, I am using the updated version of GSAS and will like to know bit more about the following feature(s)? In the histogram editing menu, What is the physical meanings of the R-free sampling factor and seed - (option S) ? How these affect the refinement result? Hope that this will n

A QUESTION ABOUT THE APD PHILIPS XRD

Dear Rietvelders, Does anybody encounter a problem stated "time out during data collection" in using the APD program of a Philips XRD system? It is annoying because the XRD will automatically stop the data collection. I checked through the manual but does not know what this about. Please advise m

Re: Siemens D500

Dear All, By the way, does anybody know where i can buy parts (eg slits) for Philips APD diffractometer (PW3710)? since this model is already out of date. Many thanks stephen Quoting James Talbot <[EMAIL PROTECTED]>: > I recommend Jim Stauver located here in Texas. His website is > http://w

Re: Problem of low-angle

users. many thanks, stephen chui Quoting William Bisson <[EMAIL PROTECTED]>: > Dear Chuisy, > > The broad bump you are experiencing at low angle may be to do with the > slits. One has to be careful with these new XRD machines which have > variable slits, to make sure

Problem of low-angle

Dear all, We are recently installing a XRD, and there is a huge peak occurred in the 3-7deg (2T) which is masking the useful signals from the sample. How can we eliminate the big peak there? We use 40kW, 30mA CuKa x-ray, divergent and receving slits are used, many thanks, stephen

Parameter file for synchrontron xray

Dear all rietvalders, I am the beginner of using synchrontron xray data for structural analyses. However i don't know whether i can use the original xry.prm file in GSAS to parameterize the synchrotron data for refinement. Please advise me Many thanks, stephen chui

Fixing parameters in GSAS

Dear all, well I do think it works ok. but i don't know why the held parameters are still there when i go back there again after doing the POWERPREF, GENLE. However, I create an new EXP file and input all things back, it resumes ok. thank you very much for your kind attention. stephen

Fixing parameters in GSAS

Dear all Rietvalders, Can anyone know how to delete the holding parameter (F option under the atomic parameter menu in GSAS)? since the program does not allow me to remove them even after pressing "D" for those variables? They are still there anyway. many thanks stephen

Fixing parameters in GSAS

Dear all Rietvalders, Can anyone know how to delete the holding parameter (F option under the atomic parameter menu in GSAS)? since the program does not allow me to remove them even after pressing "D" for those variables? They are still there anyway. many thanks stephen

trns value in GSAS

Dear All rietvalders, a question about sample transparency in GSAS is asked. is there any physical meaning when its value is positive or negative? Is the sample density correlated somehow with it? since my sample becomes less dense and the neg. trns value was obtained. Hope that it won't be too

Re: Defining the origin of P2/n

Dear Robert B.Von Dreele Thank you for your explanation. Therefore GSAS could do the origin fixing for us when the space group is not centrosymmetric. Can I boardly say that? regards, stephen

Re: Defining the origin of P2/n

Kurt > I think that P2/n has no fixed points, and in order to keep the whole > structure from shifting along the c-axis, one of the atoms has to be > arbitrarily fixed. GSAS automatically fixes the first atom z-parameter (was > your atom on the 2-fold symmetry axis?). I remember this from refini

Defining the origin of P2/n

Dear Rietvelders, I used GSAS to refine my structure in P2/n, however the program automatically fixed the the XYZ positions of the first atom during refinement. To my surprise, this atom is not seen in the "fixed atom list" in the atom parameters menu of GSAS. Please advise and many thanks, step

a question on space group

Dear all Rietcelder, Can anyboby tell me the difference between these two space groups? P63m m c and P63m c m? many thanks, stephen