Re: cif files for austenite
Hi Antonio I have tried the position of C atom, and i have supposed that could be in 8a,whic is an intersticial position, as Frank says, but you have to specify the site occupation, which is related to carbon content. Best wishes. Miguel Hesiquio On Fri, October 31, 2008 8:05 am, Frank Girgsdies wrote: Dear Antonio, as far as I know, austenite is just a solid solution of a few mole-% of carbon in gamma-iron. Thus, you essentially need the structure of gamma-Fe, which is very simple, as it is an fcc metal (space group Fm-3m, a = 3.6468 A, just one Fe atom located on 0,0,0). I found one ICSD entry for austenite. However, the dissolved carbon is placed sharing the Fe site in this structure, which I doubt makes sense from the chemical point of view. I would bet the carbon atoms are actually located on interstitial sites instead. Anyway, as we are talking about a few MOLE-% of carbon here, and carbon is much lighter than iron, I think neglecting the carbon will not make much of a difference (both for the accuracy of the calculated relative intensities and the quantification in wt-%. Thus, I would just use gamma-Fe as a replacement for austenite here. Cheers, Frank -- Frank Girgsdies Department of Inorganic Chemistry Fritz Haber Institute (Max Planck Society) -- antonio josé wrote: Dear All. I trying analyze phases in a steel sample using X-Ray technique. The analysis of X-Ray pattern shows that the main phases are ferrite and austenite. The next step would be quantify these phases by Rietveld method using TOPAS 3.0. I am looking for cif files for austenite and I didnt find it in WEB free database or in ICSD database. Do anyone has this cif file or could tell me where I can find? Thanks a lot, Antonio José [EMAIL PROTECTED]
Re: cif files for austenite
I am looking for cif files for austenite and I didnt find it in WEB free database or in ICSD database. Frank is quite correct here. Austenite is gamma-iron, which you can find immediately with Google or Wikipedia: http://en.wikipedia.org/wiki/Austenite Small amounts of carbon or hydrogen dissolved in gamma-iron, as reported in ICSD, is not going to change the X-ray pattern, since Fe-scattering will dominate. ICSD only reports what people publish. I believe the 1970 X-ray paper on austenite listed in ICSD only reports the lattice constants, and doesn't actually claim to locate the carbon. Alan. __ Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE [EMAIL PROTECTED] +33.476.98.41.68 http://www.NeutronOptics.com/hewat __
Re: cif files for austenite
The next step would be quantify these phases by Rietveld method using TOPAS 3.0. BTW, it shouldn't need a sophisticated Rietveld refinement to distinguish between the relative quantities of simple FCC and BCC compounds - some peaks may overlap almost completely, but others not at all. I worry that people rely so much on databases and computer programmes, and so little on thinking. Alan. __ Dr Alan Hewat, NeutronOptics, Grenoble, FRANCE [EMAIL PROTECTED] +33.476.98.41.68 http://www.NeutronOptics.com/hewat __
Re: cif files for austenite
Dear Antonio, as far as I know, austenite is just a solid solution of a few mole-% of carbon in gamma-iron. Thus, you essentially need the structure of gamma-Fe, which is very simple, as it is an fcc metal (space group Fm-3m, a = 3.6468 A, just one Fe atom located on 0,0,0). I found one ICSD entry for austenite. However, the dissolved carbon is placed sharing the Fe site in this structure, which I doubt makes sense from the chemical point of view. I would bet the carbon atoms are actually located on interstitial sites instead. Anyway, as we are talking about a few MOLE-% of carbon here, and carbon is much lighter than iron, I think neglecting the carbon will not make much of a difference (both for the accuracy of the calculated relative intensities and the quantification in wt-%. Thus, I would just use gamma-Fe as a replacement for austenite here. Cheers, Frank -- Frank Girgsdies Department of Inorganic Chemistry Fritz Haber Institute (Max Planck Society) -- antonio josé wrote: Dear All. I trying analyze phases in a steel sample using X-Ray technique. The analysis of X-Ray pattern shows that the main phases are ferrite and austenite. The next step would be quantify these phases by Rietveld method using TOPAS 3.0. I am looking for cif files for austenite and I didn’t find it in WEB free database or in ICSD database. Do anyone has this cif file or could tell me where I can find? Thanks a lot, Antonio José [EMAIL PROTECTED]
cif files for austenite
Dear All. I trying analyze phases in a steel sample using X-Ray technique. The analysis of X-Ray pattern shows that the main phases are ferrite and austenite. The next step would be quantify these phases by Rietveld method using TOPAS 3.0. I am looking for cif files for austenite and I didn't find it in WEB free database or in ICSD database. Do anyone has this cif file or could tell me where I can find? Thanks a lot, Antonio José [EMAIL PROTECTED]
