Rietveld Analysis of Elpidite Framework Flexibility Using in Situ Powder XRD Data of Thermally Treated Samples
Round 1
Reviewer 1 Report
The manuscript by Kostov-Kytin et al. reports a powder diffraction study of the structural transformations occurring in the microporous zirconosilicate elpidite. The approach they propose is interesting and I would suggest the manuscript for publication. However, I think that the present form must be significantly improved before final acceptance.
The first big issue is the English language: many sentences are difficult to follow (and unfortunately to understand) because of the used language style. I strongly recommend an editing of English.
From a content point of view, I suggest a major review of the following points:
- pg. 8 lines 305-307: it is not clear why in the RT powder pattern the authors wanted to test the “double-phases model”. At this temperature, only ‘’one structure’’ is supposed to be present. I would rather understand if they tested separately the Pma2 and Pbcm model, to determine which one is better. But, as far as I understood, this point is already explained and addressed in the 2.3 section..
- Table 5: Something is not clear to me in this Table. I would expect (even though the final agreement indices of structural refinements are not extremely good) that (at least) the ‘’geometric parameters’ of the structure measured at RT (row 6) were in agreement with those reported for single-crystal studies (row 2-3). The BAV for the structures reported in this study are significantly higher for tetrahedra and octahedra. Is there a reason for that? I think this point should be clarified and better explained in the discussion section.
- Table 5: when the authors report ‘’two phase study’’ (rows 8, 9): Did I understand well that the geometric parameters correspond to the most abundant phase?
- Discussion section: In this part I would also stress two additional points: 1) The interpretation of the dehydration based on the geometric parameters reported in the results section. Even if some aspects are mentioned, (e.g. lines 387-388 and lines 398-340), I would better explain the evolution of such parameters during the dehydration. 2) I would also report a more detailed comparison with previous studies, ref. 5 and Ref. 9. In addition, I would mention the work ‘’V. Nedel’ko, N.V. Chukanov, I.V. Pekov, Inorg. Mater. 47 (5) (2011) 502e505’’ where the authors investigated the dehydration kinetic of elpidite from Lovozero. If I am not wrong, this study is not cited in the manuscript, though I think a comparison could be interesting.
Additional comments refer to:
- pg. 4 lines 156-159: I would report the description of picture 2 in the figure caption.
Materials and methods:
- Was the powder insert in a capillary? Or was it deposited on a sample holder (silicon?)
- Why no absorption correction was used?
Results:
- pg. 7 line276: the 022 reflection is actually very strong also in Pbcm, isn’t it?
- pg. 8 line292: did the authors mean “refinements” instead of measurements?
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The presented research focuses on the study of Elpidite structure (mineral). Using a temperature test of Powder X-ray Difraction and The Rietveld refinement procedure to determine the initial structure of the material. Additionally were calculated changes in the unit cell due to thermal treatment. Author used advanced methods and calculations to determine the material structure. However, he composition od the manuscript seems to be disturbed. In my opinion this manuscript need the several major changes and improvements according to the following reasons:
Page 2/ line 48 – I do not think that such comments are necessary. The construction of the articles forces the appropriate place of information.
Page 2/ lines 83-86 - The possibilities of the Rietveld's method for studying the structure of minerals, metals and their alloys or ceramic materials have been known since the seventies, hence the aim of this work is not justified and does not reflect the scope of the work. More accurate are sentences on page 4/ line 150-152. The information about the scope should be at the end of Introduction od section to clearly summaries the theoretical introduction.
Page 2/line 86 to page5/ line 180 - The summary of previous studies into the Introduction section seems unnecessary. This information and studies provided may significantly enrich discussion of the results.
Page 6/ line 191 -Please consider if heating to such temperatures in air cannot cause oxidation of the material
Page 6/ lines 192-193 - Please explain why these measurement temperatures were chosen. Have DSC or TGA tests been carried out before to determine transition temperatures?
Page 6/ lines 196-197 – Did the Authors use the diffraction line position pattern? If yes, what pattern was used?
Page 6/ lines 211-220 - This is no place for such a comment. I think we can make it rich discussion section.
Page 7/ line 241 - It is enough that this information is mentioned in the bibliography
Page 7/ lines 272 – 282 - It seems more readable to include the phase identification of these two structures. I understand that the selected peaks have been analyzed. However, I think it is necessary to determine a minimum of 3 characteristic peaks for the phase identification.
Page 8/ Figure 3 - The figure seems to be unclear if we are thinking about analysis of the position of the individual peaks. It would be advisable to include additional figures of the peaks in a small angular range. For example 26-30º2θ. It will better represent the changes of peak profile and position.
Page 9/ Figure 4 – Unfortunately, the figures are poor quality. They are gray and the information are unreadable.
Page 10/ line 322 – Please, delete this comment.
Page 11/ table 2 – Please explain why the Authors assumed that 100 percent of the one position is fill by one type of atom (site of occupancy factor). For such minerals with complicated structure it is normal to have substituted atoms. This is the reason for deviations in unit cell parameters, changes of peaks intensity etc.
Please support your decision by literature.
Page 17 – Please consider a separate section for a short conclusion. Conclusions are lost in this section. The summary should be concise and reflect/ support the aim of the work.
The discussion of results seems to be limited, it would be beneficial to enrich it. Especially since there are many interesting literary references in the previous paragraphs that could enrich the discussion.
Page 18 – The references should be corrected. The positions have different formats.
Please consider enriching the publication with studies of the chemical composition of the material for example XRF method. Minerals may be contaminated by other elements such as Ni, C, F, Cl, which may affect the structure of the material (especially parameters of unit cell).
There is no information about identified phase (except the space group). It will be better to enclose information such as unit cell parameters and number of ICDD.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 3 Report
Very good and interesting paper with clear presentation and analysis of the obtained results. The ms can be accepted for publication after minor revisions.
- The authors have two structure models, Pbcm and Cmce. How do they relate to each other? I suggest that the authors re-name topologically identical atoms of the framework to bear the same designations and provide the values of the respective Zr-O-Si and Si-O-Si valence angles for comparison (for their models only, not for literature data). These data can be provided as Supplementary Material, for example.
- The zirconosilicate framework responds to the removal of H2O from its channels, obviously due to the reconfiguration of the bonding system between extraframework species (Na+ cations, in particular) and the framework itself. Which O atoms of the frameworks are most influenced by the removal of H2O and formation of new Na-O bonds? The analysis of these interactions would be very useful and the recommendation in (1) may help to figure it out more clearly.
- Some language polishing would be welcome. E.g., in places like this:
81-82:
Both these works turn attention to the impact of the dehydration processes on the occurring upon it structural transformations of the studied material.
Unclear. Please re-phrase.
4. Table 2: O atoms of the H2O molecules should be clearly identified.
Author Response
Please see the attachment
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
I found that the manuscript is now more understandable.
Minor english spell I found at:
pg 3 line 63: "realte" should be "relates"
pg. 19 line 423: "indicate" should be "indicates"
pg.20 line 461: the sentence may be rearranged in "Some of the measured twist angles in this study.."
Reviewer 2 Report
Dear Authors,
I really appreciate the scientific discussion we had about the manuscript. I am glad that we managed to reach a compromise.
I wish you scientific success.
