Dear RG experts
For a particular compound, we have many standard XRD JCPDS card numbers having similar peak positions/ diffraction planes/ intensities. What is the difference between them or what is the significance of having many standard JCPDS card numbers?
Thank you
Dear guys...in principle you are more or less right, but you need to consider the meaning of database. This is only a collection of data published somewhere. Any evaluation is impossible, i.e. only obvious errors are discovered and such data are excluded. This means, that not the newest is the best. It should be the best since our equipment is nowadays better, but we do not work that properly anymore than 30 to 50 years ago, where only experts published papers. Nowadays, everybody who is able to write can publish something which is hard to evaluate. Moreover, many claimed materials are naturally doped or artificially polluted so that lattice parameters as well as intensities can vary (texture). This can be, however, also the results of improperly used software. There are so many correcting term introduced that you can compensate everything if you do not exactly know what you are doing. Therefore, PDF (JCPDS does not exisr anymore for a long time!) data are a good hint, but it is hard to define, which description is the correct. This also explains, why so many descriptions of the same phase is listed.
Summary : a database is only a collection of data. There is no suitable voting since obviously wrong data would not be listed.
Dear Elangbam,
You can follow anyone of the available JCPDSs. Sometimes, for a particular compound there may have different crystal phases. This is why for that particular compound there should have different JCPDS. In case of a single phase compound there may have more than one JCPDS which were reported by different group at different time. Nothing else.
Thank you.
Thank you Dr Anup for the answer. I have seen many numbers for the same phase (structure) in many papers as well as standard cards. They are all acceptable so, I was just searching to have idea that it is only a reference number which is essential or any other significant parameter.
With best regards
First I want to clarify... I'm not Dr not yet. You can take anyone of the available JCPDSs. But it should be better to accept the recent one. The recent one may have some update(s) or clarification(s) if any. Thank you and all the best.
Dear Chitra,
I agree with the above comments. Also i would like to mention here that, for particular crystal structure of a compound/element, there will have many standard diffraction patterns available in the data base. When you try to compare your own data with the standard one, it is also important to know under which conditions the diffraction data (JCPDS) of the samples were collected. if that matches with your experimental conditions, then that JCPDS data could serve you the best for comparison.
Dear Anup
Thank you for the kind suggestions and clarification.
Best wishes
Dear Dr Irshad
Thank you so much for the kind suggestions. One more thing that I observe here i.e., multiple ref nos. and updates is inability to compare our results with previous literature reports which I think sometimes becomes essential to support my result. So, can you suggest some idea how these old and new updates are connected? Or any other related important informations?
With best regards
Dear guys...in principle you are more or less right, but you need to consider the meaning of database. This is only a collection of data published somewhere. Any evaluation is impossible, i.e. only obvious errors are discovered and such data are excluded. This means, that not the newest is the best. It should be the best since our equipment is nowadays better, but we do not work that properly anymore than 30 to 50 years ago, where only experts published papers. Nowadays, everybody who is able to write can publish something which is hard to evaluate. Moreover, many claimed materials are naturally doped or artificially polluted so that lattice parameters as well as intensities can vary (texture). This can be, however, also the results of improperly used software. There are so many correcting term introduced that you can compensate everything if you do not exactly know what you are doing. Therefore, PDF (JCPDS does not exisr anymore for a long time!) data are a good hint, but it is hard to define, which description is the correct. This also explains, why so many descriptions of the same phase is listed.
Summary : a database is only a collection of data. There is no suitable voting since obviously wrong data would not be listed.
Dear Dr Gert Nolze
Thank you so much Sir for the elegant answer. It is really very nice to have such an important information.
With best regards
Chitra
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