Re: [sdpd] Re: Are restraints as good as observations ?
All deviations from expected values (1.514 and 1.634) are within 3 e.s.u.s that are around 0.03 A in average. About absurdity, there are different sensibilities... With such a definition above, 1.72(3) instead of 1.634 is just OK for Leonid. Where would he see a limit before applying restraints ? Never, since he will find also that 1.9(1) is quite excellent, or even 2.2(3) : all deviations are within 3 e.s.u.s. I mean, Leonid refuse to see any reliability limit to the powder results. Absurdity does not exist at all for him (with the exception of mine apparently). The difference between us is that I am happy with 1.634(2) but already think that soft restraints are clearly needed when I have 1.72(3). This is all my crime... Best, Armel ++ Please do NOT attach files to the whole list alan.he...@neutronoptics.com Send commands to lists...@ill.fr 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: Precision of lattice parameters
Hello Ahmed. It depends on the method you use. For Rietveld, you need quite a lot of parameters, i.e., both sample (structural) parameters and instrumental parameters. Regarding the first group, you have diadochy and defects, that make your sample (or its components) differ from the standards you need to use. But that's what Rietveld does: calculates this difference. More problematic is the way you prepare the sample: the more isogranular is the sample, the better results (i.e., less corrections need to be done by the computer). Also, there is preferred orientation, but this counts for quantitative analysis results rather than unit cell parameters. Regarding instrumental parameters, these are especially the Lorentz-polarization effect, zero of the detector shift (which is physically equal, more or less, to sample displacement - thus, these two parameters CANNOT be used together in any refinement). In general, the better is the sample preparation, the better results you have. Good luck! Lukasz Kruszewski Dear Rietvelders, I am working on the precise measurement of lattice parameters using X-ray diffraction data. Please let me know: 1. Precautions taken during the data recording using XRD. 2. How can we calculate lattice parameters precisely with in the 1x 10-5 nm. 3. It is well known that XRD gives some % of errors, what is the reason behind these errors. Thankyou very much for your time. -- *Dr. Faheem Ahmed * *Post Doc Fellow*- *Engineering Research Centre (ERC)* *School of Nano and Advanced Materials Engineering, Building. No. 54, Room- 322 Changwon National University, # 9 Sarim-dong, Changwon, Gyeongnam 641-773, * *Republic of Korea.* *Email:* faheem...@gmail.com *Ph No*. 0082-55-264-5431 (Office) 0082-10-7263-6411 (Mobile) -- Łukasz Kruszewski, Ph.D., adjunct Polish Academy of Sciences Institute of Geological Sciences X-Ray Diffraction Laboratory (coordinator) Twarda 51/55 str. 00-818 Warsaw Poland ++ Please do NOT attach files to the whole list alan.he...@neutronoptics.com Send commands to lists...@ill.fr 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: [sdpd] Re: Are restraints as good as observations ?
I mean, Leonid refuse to see any reliability limit to the powder results. Absurdity does not exist at all for him (with the exception of mine apparently). The difference between us is that I am happy with 1.634(2) but already think that soft restraints are clearly needed when I have 1.72(3). This is all my crime... Absurdity or credibility of results depends on the research purpose. For some purposes 1.72(3) may be OK if (3) is realistic, for other purposes even 1.634(2) will be absurd especially if (2) is artificial. If you have a magic for a universal assessment of absurdity then this is one more Know How and I may only humbly unbonnet. I think that Alan is right in that we should stop this thread since we reach such high matters as absurdity and crime. *** Leonid A. Solovyov Institute of Chemistry and Chemical Technology 660049, K. Marx 42, Krasnoyarsk, Russia http://sites.google.com/site/solovyovleonid *** From: Armel Le Bail x...@noos.fr To: s...@yahoogroups.com Cc: rietveld_l@ill.fr Sent: Friday, August 2, 2013 2:37 PM Subject: Re: [sdpd] Re: Are restraints as good as observations ? All deviations from expected values (1.514 and 1.634) are within 3 e.s.u.s that are around 0.03 A in average. About absurdity, there are different sensibilities... With such a definition above, 1.72(3) instead of 1.634 is just OK for Leonid. Where would he see a limit before applying restraints ? Never, since he will find also that 1.9(1) is quite excellent, or even 2.2(3) : all deviations are within 3 e.s.u.s. I mean, Leonid refuse to see any reliability limit to the powder results. Absurdity does not exist at all for him (with the exception of mine apparently). The difference between us is that I am happy with 1.634(2) but already think that soft restraints are clearly needed when I have 1.72(3). This is all my crime... Best, Armel ++ Please do NOT attach files to the whole list alan.he...@neutronoptics.com Send commands to lists...@ill.fr 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/ ++
[no subject]
All deviations from expected values (1.514 and 1.634) are within 3 e.s.u.s that are around 0.03 A in average. About absurdity, there are different sensibilities... With such a definition above, 1.72(3) instead of 1.634 is just OK for Leonid. Where would he see a limit before applying restraints ? Never, since he will find also that 1.9(1) is quite excellent, or even 2.2(3) : all deviations are within 3 e.s.u.s. Obviously that 1.9(1) and 2.2(3) are much worse than 1.72(3). Relative error (sigma/bondlenth) for them are 0.1/1.9=0.053=5.3% and 0.3/2.2=0.137=13.7%! But 1.72(3) has 0.03/1.72 =0.017=1.7% - seems to be good. Best wishes, Maxim ++ Please do NOT attach files to the whole list alan.he...@neutronoptics.com Send commands to lists...@ill.fr 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: [sdpd] Re: Are restraints as good as observations ?
I think that Alan is right in that we should stop this thread since we reach such high matters as absurdity and crime. The end words can be the following : Most journals have place for supplementary materials. May be even Leonid could be happy if three tables were presented, 1- the raw Rietveld refinement with all parameters free, 2- results with soft restraints or rigid body if the author finds some magic to decide to use them, 3 - DFT results. And maybe a fourth table will be required in case of the presence of H atoms since recently Leonid seems to recognize that DDM sometimes needs for fully constrain hydrogen atoms (remember the previous discussion at the Rietveld list where he claimed that all H can be seen and refined independently, always). So, Are restraints as good as observations ? Certainly not, but powder observations are so bad in complex cases that restraints may be admitted, and even constraints for H atoms. Not sure that your young students have received a complete formation if they have to argue Even Armel Le Bail has to apply restraints!. Well, yes, even not ashamed. Best, Armel ++ Please do NOT attach files to the whole list alan.he...@neutronoptics.com Send commands to lists...@ill.fr 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: [sdpd] Re: Are restraints as good as observations ?
remember the previous discussion at the Rietveld list where he claimed that all H can be seen and refined independently, always. Absurd - never said so. From absurdity and crimes we arrived at falsifications? Not sure that your young students have received a complete formation if they have to argue Even Armel Le Bail has to apply restraints!. Hope my formation is still far from completion, too. Not the Best, Leonid *** Leonid A. Solovyov Institute of Chemistry and Chemical Technology 660049, K. Marx 42, Krasnoyarsk, Russia http://sites.google.com/site/solovyovleonid *** From: Armel Le Bail x...@noos.fr To: rietveld_l@ill.fr rietveld_l@ill.fr Cc: s...@yahoogroups.com s...@yahoogroups.com Sent: Friday, August 2, 2013 4:39 PM Subject: Re: [sdpd] Re: Are restraints as good as observations ? I think that Alan is right in that we should stop this thread since we reach such high matters as absurdity and crime. The end words can be the following : Most journals have place for supplementary materials. May be even Leonid could be happy if three tables were presented, 1- the raw Rietveld refinement with all parameters free, 2- results with soft restraints or rigid body if the author finds some magic to decide to use them, 3 - DFT results. And maybe a fourth table will be required in case of the presence of H atoms since recently Leonid seems to recognize that DDM sometimes needs for fully constrain hydrogen atoms (remember the previous discussion at the Rietveld list where he claimed that all H can be seen and refined independently, always). So, Are restraints as good as observations ? Certainly not, but powder observations are so bad in complex cases that restraints may be admitted, and even constraints for H atoms. Not sure that your young students have received a complete formation if they have to argue Even Armel Le Bail has to apply restraints!. Well, yes, even not ashamed. Best, Armel++ Please do NOT attach files to the whole list alan.he...@neutronoptics.com Send commands to lists...@ill.fr 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: [sdpd] Re: Are restraints as good as observations ?
At 03:04 02/08/2013 -0700, Leonid Solovyov wrote: remember the previous discussion at the Rietveld list where he claimed that all H can be seen and refined independently, always. Absurd - never said so. From absurdity and crimes we arrived at falsifications? Below are the unfalsified words. Ugly yours, with pestilence, Armel PS- rigid brain is the first step before rigid body = Subject: DDM program update 1.92 Date: Sun, 16 Oct 2011 20:41:12 -0700 (PDT) From: Leonid Solovyov l_solov...@yahoo.com To: rietveld_l@ill.fr Dear Colleagues, The DDM program update 1.92 with some minor bugs fixed is available at http://sites.google.com/site/ddmsuite/ and http://l-solovyov.narod.ru/ddm.html The folder EXAMPLES\H-atoms\ now contains 15 instances of unconstrained refinement of H-atoms from XRPD data of various quality and complexity. A good illustration to the recent SDPD discussion on H-atoms and restraints is the structure of C7H6ClN3O4S2 that was refined previously by a restrained Rietveld using a combination of XRD and neutron data [Acta Cryst. B (2008) 101]. By DDM it is refined from XRD data solely without restraints including 6 independent H-atoms [EXAMPLES\H-atoms\C7H6ClN3O4S2.ddm]. In the alternations of C-C and C-N distances and angles the alternations of singe and double bonds is correctly reproduced. Apparently, H-atoms are not a plague and a curse, but the extensive use of restraints is a real disease of powder diffraction. Beside all other consequences, this pestilence diminishes the value of the method giving it a reputation of a speculative technique. Don't restrain, be free! Leonid *** Leonid A. Solovyov Institute of Chemistry and Chemical Technology 660049, K. Marx 42, Krasnoyarsk, Russia http://sites.google.com/site/solovyovleonid *** ++ Please do NOT attach files to the whole list alan.he...@neutronoptics.com Send commands to lists...@ill.fr 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: [sdpd] Re: Are restraints as good as observations ?
Thanks for the correct citation where the term “always” is definitely absent. A bit Better, Leonid *** Leonid A. Solovyov Institute of Chemistry and Chemical Technology 660049, K. Marx 42, Krasnoyarsk, Russia http://sites.google.com/site/solovyovleonid *** From: xtal x...@noos.fr To: rietveld_l@ill.fr rietveld_l@ill.fr Cc: s...@yahoogroups.com Sent: Friday, August 2, 2013 5:25 PM Subject: Re: [sdpd] Re: Are restraints as good as observations ? At 03:04 02/08/2013 -0700, Leonid Solovyov wrote: remember the previous discussion at the Rietveld list where he claimed that all H can be seen and refined independently, always. Absurd - never said so. From absurdity and crimes we arrived at falsifications? Below are the unfalsified words. Ugly yours, with pestilence, Armel PS- rigid brain is the first step before rigid body = Subject: DDM program update 1.92 Date: Sun, 16 Oct 2011 20:41:12 -0700 (PDT) From: Leonid Solovyov l_solov...@yahoo.com To: rietveld_l@ill.fr Dear Colleagues, The DDM program update 1.92 with some minor bugs fixed is available at http://sites.google.com/site/ddmsuite/ and http://l-solovyov.narod.ru/ddm.html The folder EXAMPLES\H-atoms\ now contains 15 instances of unconstrained refinement of H-atoms from XRPD data of various quality and complexity. A good illustration to the recent SDPD discussion on H-atoms and restraints is the structure of C7H6ClN3O4S2 that was refined previously by a restrained Rietveld using a combination of XRD and neutron data [Acta Cryst. B (2008) 101]. By DDM it is refined from XRD data solely without restraints including 6 independent H-atoms [EXAMPLES\H-atoms\C7H6ClN3O4S2.ddm]. In the alternations of C-C and C-N distances and angles the alternations of singe and double bonds is correctly reproduced. Apparently, H-atoms are not a plague and a curse, but the extensive use of restraints is a real disease of powder diffraction. Beside all other consequences, this pestilence diminishes the value of the method giving it a reputation of a speculative technique. Don't restrain, be free! Leonid *** Leonid A. Solovyov Institute of Chemistry and Chemical Technology 660049, K. Marx 42, Krasnoyarsk, Russia http://sites.google.com/site/solovyovleonid ***++ Please do NOT attach files to the whole list alan.he...@neutronoptics.com Send commands to lists...@ill.fr 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/ ++
Restraints on posting to the Rietveld list
From absurdity and crimes we arrived at falsifications? Ugly yours, with pestilence, PS- rigid brain is the first step before rigid body OK, I asked people to stop this argument. The essential points have been covered, so I am restraining the two principal antagonists from posting for a 1 week relaxation period :-) Please email me personally if you don't agree. __ Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE alan.he...@neutronoptics.com +33.476.98.41.68 http://www.NeutronOptics.com/hewat __ ++ Please do NOT attach files to the whole list alan.he...@neutronoptics.com Send commands to lists...@ill.fr 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: Help with parts for of an old Philips 1055/81 goniometer ?
Thanks to all who replied about this, and in particular to those who offered parts and suggested that Hiltonbrooks (UK) had such spare parts for old equipment - http://www.xrays.u-net.com. My colleague now thinks his workshop might be able repair the original piece, so is holding off on following up on your suggestions that I forwarded to him. Alan On 1 August 2013 01:08, Alan Hewat alan.he...@neutronoptics.com wrote: A colleague asks if anyone can help him with the rotating sample compartment of an old Philips 1055/81 goniometer ? He badly needs this part since the company (Panalytical) say they no longer support this very old system. __ Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE alan.he...@neutronoptics.com +33.476.98.41.68 http://www.NeutronOptics.com/hewat __ ++ Please do NOT attach files to the whole list alan.he...@neutronoptics.com Send commands to lists...@ill.fr 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/ ++
