Re: Neutron diffraction with boron
Armel wrote: And yes, the measurements have been done. I would not call Science giving the MgB2 atomic coordinates, already known. Was this meant to be serious? Checking for any subtle structural changes around Tc would be (has been?) a worthwhile investigation. Something easily worthy of the word "science", as I understand it. Knowing what the structure does or doesn't do around the transition would be a prerequisite to a deeper understanding of the phenomena. Apologies if it's just that my sense of irony has been in remission this morning. Jon
Re: Neutron diffraction with boron
Knowing what the structure does or doesn't do around the transition would be a prerequisite to a deeper understanding of the phenomena. We still wait for a deeper understanding of the phenomena, since 1986, right ? And this, after thousands of characterizations. You really think that MgB2 will give more ? Maybe... More probably not. Anyway, I completely agree about the fact that this has to be done : just routine to do so. Armel
Re: Neutron diffraction with boron
You really think that MgB2 will give more ? Maybe... just routine to do so. Armel, it was you who asked if boron was possible with neutrons, and when you are told that it is, you say that anyway it is borin' (excuse the pun :-) Well, let me predict the future of the coming paper : high citation level guaranteed If you know how to guarantee high citation levels, go to it :-) Alan. Dr Alan W. Hewat, Diffraction Group Leader. Institut Laue-Langevin Grenoble FRANCE [EMAIL PROTECTED] fax (33)4.76.20.76.48 tel (33) 4.76.20.72.13 (or .26 Mme Guillermet) http://www.ill.fr/dif/AlanHewat.htm
Re: Neutron diffraction with boron
If you know how to guarantee high citation levels, go to it :-) Alan, you already occupy the place of leader of the Group of Crystallography at ILL, the best neutron reactor for research in the world ;-). Knowing how cannot ensure to succeed... There are a few other parameters to refine. Armel
Re: Neutron diffraction with boron
At 04:48 PM 3/29/01 +0200, you wrote: You really think that MgB2 will give more ? Maybe... just routine to do so. Armel, it was you who asked if boron was possible with neutrons, and when you are told that it is, you say that anyway it is borin' (excuse the pun :-) I hadn't realised there was any problem with x-rays together with magnesium and boron ;) Apologies for my previous mail (Re: new gsas), which wasn't supposed to go to the list, probably this one shouldn't either, but anyway: Refining a silicon standard is a routine and fairly dull thing to do, but it is necessary. Being the first group to systematically study the structure of an unexpected superconductor above, below and around it's transition temperature does not really fall into the 'routine' category. Is it really worth trying to belittle what should turn out to be excellent science? Jon
Re: Neutron diffraction with boron
Is it really worth trying to belittle what should turn out to be excellent science? A serendipity case. Once more. Where is excellency exactlly, according to you ? I repeat that excellency would be to produce a theory which would have allowed to predict the MgB2 superconductor properties. Then, the need for chance in order to disclose it would have been unnecessary. I would call that excellent chance, not excellent science. I think I can make the difference. I admit that the authors should receive congratulations for their phenomenal chance. After all, this compound is known structurally since several decades. The conclusion is that we still continue to need having chance for discovering new superconductors, because a good global scientific theory is still lacking. Others have no chance at all, or no equipment. The producers of the first copper oxyde supraconductor were clearly unlucky, though making good science for chemists (also traditionally unable to predict what will be obtained when putting given elements in a platinum tube at high temperature). An extraordinary discovery is not necessarily Science. It is just an unexpected result. Wow, lucky guys ! Splendid ! Now give the sample to neutronists, but please with the good B isotope, and see what happens. Best regards, Armel
Re: Neutron diffraction with boron
Is it really worth trying to belittle what should turn out to be excellent science? A serendipity case. Once more. Where is excellency exactlly, according to you ? I repeat that excellency would be to produce a theory which would have allowed to predict the MgB2 superconductor properties. Then, the need for chance in order to disclose it would have been unnecessary. "Chance favours the prepared mind" - Louis Pasteur ??? but "Non est ars quae ad effectum casu venit" (That which achieves its effect by accident is not art) Seneca, the Younger (4 B.C. - A.D. 65) Though if serendipity was not allowed in science? Lachlan. Lachlan M. D. Cranswick Geochemistry - Lamont-Doherty Earth Observatory, Columbia University PO Box 1000, 61 Route 9W Palisades, New York 10964-1000 USA Tel: (845) 365-8662 Fax: (845) 365-8155 E-mail: [EMAIL PROTECTED] WWW: http://www.ldeo.columbia.edu CCP14 Xtal Software Website: http://www.ccp14.ac.uk
Re: Neutron diffraction with boron
Dang... I'm glad that we didn't have to wait for excellent science to theoretically predict penicillin for us. Absolutely ! The whole humanity is lucky that things to be found, whatever, are discovered times to times. Fire, the wheel, who remember the inventors ? But our era is lacking of modesty, at least. "Excellent science" are terms tending to lose any sense. All scientists need to be recognized as being excellent, no less, for not being fired (exceptions are at the CNRS, France where we are continuously excellent for all our life, of course, and so, never fired ;-) and for continuing to get grants. Today, nobody can pretend to be a real "savant", because embracing the whole human knowledge is impossible for a simple human being. Who was the truly last "savant" ? Newton , Diderot ? And who are we today ? Excellent scientists, probably, but no more ;-). Nobody will remember of us, millions of excellent scientists, in 200 years, or sooner. This could be the beginning of a poem : "But where are the savants of the yesteryears ?" Armel
RE: Neutron diffraction with boron
With regard to MgB2 and atomic coordinates 1) Armel's rightit's routine work at this day age. 2) I also agree that atomic coordinates is a prerequisite for deeper understanding etc etc. My views on this matter however: No crystal structure can make a living as a crystal structure :-( It's the properties that need be harnessed. Once the structure is solved...the immediate question should be...so what? :-) If you can come up a useful answer to that, than you're at the very beginning of a very exciting "science" study which may ultimately lead to an engineering success. That's of course my opinion, I could be wrong--to coin a line from the 400 lbs Gorilla (aka Dennis Miller) E. K. Akdogan, Ph. D. Research Associate Center for Ceramic Research Rutgers University 607 Taylor Road Piscataway, NJ 08854-8065 Phone: (732)-445 5614 Fax: (732)-445 5577 E-mail : [EMAIL PROTECTED] -Original Message- From: Armel Le Bail [mailto:[EMAIL PROTECTED]] Sent: Thursday, March 29, 2001 6:26 AM To: [EMAIL PROTECTED] Subject: Re: Neutron diffraction with boron Knowing what the structure does or doesn't do around the transition would be a prerequisite to a deeper understanding of the phenomena. We still wait for a deeper understanding of the phenomena, since 1986, right ? And this, after thousands of characterizations. You really think that MgB2 will give more ? Maybe... More probably not. Anyway, I completely agree about the fact that this has to be done : just routine to do so. Armel
RE: Neutron diffraction with boron
Well...the question: So what? inherently contains "Structure-Property Relations" indeed. I thought the message was tacitly conveyed. It seems I was wrong. Regards E. K. Akdogan, Ph. D. Postdoctoral Associate Center for Ceramic Research Rutgers University 607 Taylor Road Piscataway, NJ 08854-8065 Phone: (732)-445 5614 Fax: (732)-445 5577 E-mail : [EMAIL PROTECTED] -Original Message- From: Peter Y. Zavalij [mailto:[EMAIL PROTECTED]] Sent: Thursday, March 29, 2001 4:41 PM To: [EMAIL PROTECTED] Subject: RE: Neutron diffraction with boron "Crystal structure ... is the properties ..." It does not sound right but "very exiting "science"" is to find link between the crystal structure and the properties... Peter Zavalij -Original Message- From: E. K. Akdogan [mailto:[EMAIL PROTECTED]] Sent: Thursday, March 29, 2001 4:29 PM To: [EMAIL PROTECTED] Subject: RE: Neutron diffraction with boron Importance: High With regard to MgB2 and atomic coordinates 1) Armel's rightit's routine work at this day age. 2) I also agree that atomic coordinates is a prerequisite for deeper understanding etc etc. My views on this matter however: No crystal structure can make a living as a crystal structure :-( It's the properties that need be harnessed. Once the structure is solved...the immediate question should be...so what? :-) If you can come up a useful answer to that, than you're at the very beginning of a very exciting "science" study which may ultimately lead to an engineering success. That's of course my opinion, I could be wrong--to coin a line from the 400 lbs Gorilla (aka Dennis Miller) E. K. Akdogan, Ph. D. Research Associate Center for Ceramic Research Rutgers University 607 Taylor Road Piscataway, NJ 08854-8065 Phone: (732)-445 5614 Fax: (732)-445 5577 E-mail : [EMAIL PROTECTED] -Original Message- From: Armel Le Bail [mailto:[EMAIL PROTECTED]] Sent: Thursday, March 29, 2001 6:26 AM To: [EMAIL PROTECTED] Subject: Re: Neutron diffraction with boron Knowing what the structure does or doesn't do around the transition would be a prerequisite to a deeper understanding of the phenomena. We still wait for a deeper understanding of the phenomena, since 1986, right ? And this, after thousands of characterizations. You really think that MgB2 will give more ? Maybe... More probably not. Anyway, I completely agree about the fact that this has to be done : just routine to do so. Armel
Neutron diffraction with boron
Armel Le Bail wrote: Have new neutron powder patterns been done on the magnesium diboride superconductor yet (or derivatives, if any), or B absorption will be a too big problem ? Yes, neutron absorption by boron is a potential problem, however use of 11B in place of natural abundance boron eliminates the absorption. This isotope is available fairly readily. And yes, the measurements have been done. People contemplating neutron experiments may want to estimate absorption using http://www.ncnr.nist.gov/xtal/neutron.html Brian News Flash: The unscheduled mantainence for the NIST reactor has been postponed until our scheduled upgrade in August. We plan to resume operations in about 2 weeks. Brian H. Toby, Ph.D.Leader, Crystallography Team [EMAIL PROTECTED] NIST Center for Neutron Research, Stop 8562 voice: 301-975-4297 National Institute of Standards Technology FAX: 301-921-9847Gaithersburg, MD 20899-8562 http://www.ncnr.nist.gov/xtal
RE: Neutron diffraction with boron aka Genie in the bottle
With regards to MgB2... Is the crystallographic (structural) data for that ceramic published. I'd appreciate it if someone could provide me with the bibliographical info at his/her convenience. Thanks in advance, Koray E. K. Akdogan, Ph. D. Research Associate Center for Ceramic Research Rutgers University 607 Taylor Road Piscataway, NJ 08854-8065 Phone: (732)-445 5614 Fax: (732)-445 5577 E-mail : [EMAIL PROTECTED] -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Brian H. Toby Sent: Wednesday, March 28, 2001 11:01 AM To: [EMAIL PROTECTED] Subject: Neutron diffraction with boron Armel Le Bail wrote: Have new neutron powder patterns been done on the magnesium diboride superconductor yet (or derivatives, if any), or B absorption will be a too big problem ? Yes, neutron absorption by boron is a potential problem, however use of 11B in place of natural abundance boron eliminates the absorption. This isotope is available fairly readily. And yes, the measurements have been done. People contemplating neutron experiments may want to estimate absorption using http://www.ncnr.nist.gov/xtal/neutron.html Brian News Flash: The unscheduled mantainence for the NIST reactor has been postponed until our scheduled upgrade in August. We plan to resume operations in about 2 weeks. Brian H. Toby, Ph.D.Leader, Crystallography Team [EMAIL PROTECTED] NIST Center for Neutron Research, Stop 8562 voice: 301-975-4297 National Institute of Standards Technology FAX: 301-921-9847Gaithersburg, MD 20899-8562 http://www.ncnr.nist.gov/xtal
