I am working on the high pressure (structural and vibrational) studies on strong spin orbit coupling materials. One of my material show phase transition (new structure) under pressure. I have indexed the obtained peak positions with the help of powd software. The indexed values (lattice parameter, angle, and volume) for the particular crystal system (possible) are listed as output in the program.
But, how can I identify the space group of the structure? Is there any software for identifying the structure (space group) of the compounds? Kindly help me to find out the space group of unknown structure.
Peak positions - or better - reflection positions tell you someting about the translation lattice but not more. There are phases which are triclinic but described by a cubic lattice so that the reflection positions look like cubic but they are not. in order to get information about the crystal STRUCTURE absent reflections (zero intensities) need to be analyze. If they are at the same positions as other reflections of non-zero intensities it is hard to evaluate the intensity. Therefore, only in very rare cases you can reliably extract the space-group symmetry from a powder diffractogram. Only, if you know the structure roughly you can try to get a refinenement of existing data. Only by special assumptions (which might be wrong) you can solve this problem which might work sometimes but not in general. You have to be careful...also with the indexing since the lattice could be a pseudo-lattice and you don't recognize small-intensity reflections which are only a bit higher than the noise.
Dear Gert Nolze
Thank you for the suggestion. Based on the structural prototype system, we are assuming the structure is monoclinic. Can you please suggest some indexing software to get the correct space group out monoclinic space groups?
Hello, Rajaji Vincent. I would like to offer you that EXPO2004 program and its tutorial. You can download it from below link:
https://www.4shared.com/rar/eRcry9tgca/EXPO2014.html
I hope it can help your job.
Please open the below link of article; http://dx.doi.org/10.13140/RG.2.2.27720.65287/3, which practically explains the structures of different materials; structural analyses of different materials validate new atomic structures; study further discusses that crystalline materials do not require primitive cells in order to explain the structures and the distance between electronic states is relevant rather than the lattice constant; study reveals the preliminary detail of crystallinity, non-crystallinity, porosity, texture and noise factors along with overall characteristics of peaks; study further categorizes the residual and thermal stresses; shift in peak, hkl values, Miller Indices, planes, d-spacing, Bragg diffraction, Scherrer equation, pdf card are also explained in this study. Overall, the study suggests to re-investigate the materials at all scales. (This article is not peer reviewed yet.)