Giant Premelting Effects for Solid–Liquid Discontinuous Transition in Nitrobenzene under Compression

Round 1

Reviewer 1 Report

Investigation of phenomena associated with phase transitions is a challenging topic from the experimental and theoretical points of view. On the one side, carefully designed experiments are necessary. On the other, thermodynamics of non-equilibrium process and mechanistic models are much more difficult than the “standard” equilibrium formulations. The manuscript on “Giant Premelting Effects for Solid-Liquid Discontinuous Transition in Nitrobenzene under Compression” by Kalabiński, Drozd-Rzoska and Rzoska is an interesting contribution to this field of research. I deem it worthy of publication in the Crystals journal, however there is need for some modifications. I consider them a minor revision, because they concern the presentation issues, and apart from them I have only one small request regarding the scientific value of the manuscript.

The first, scientific issue is as follows. The authors do not provide detailed mechanistic insight into the observed anomaly, apart from the reference to a probable mechanism of “‘crushing’ crystalline grains by isotropic squeezing and increasing liquid layers between grains”. My question is: are there also more molecular explanations? Is it possible that some local reordering, molecular reorientation etc. takes place? Should such explanations be rather excluded and if so, why? The discussion around the line 492 of Conclusions should be enhanced to this effect.

The discussion is in most parts very general. The numerical data (fitting to the equations) are provided in Figures 1, 2, 5 and 6, but not extensively discussed or compared with data for other compounds (if available). On the other hand, I cannot see the steepness index equation parameters. Please provide some comment on the possibility (or non-possibility) of extended discussion of the fitted parameters. There are some hints at such discussion, e.g. line 438: “with values of critical exponents indicating the classical, mean-field type description”, and they should be somewhat enlarged.

Moreover, the role of Figures 7 and 8, together with associated data, is not clear. Do they really belong to Materials and Methods? Are they necessary only to show the purity of material, accuracy of measurements etc.? Maybe they should be placed in the Results section and discussed?

Other issues are rather minor:

The beginning of Results and Discussion (line 161 and onwards) is very didactical, which is positive, but its value could be enhanced by mentioning at this point that the “dielectric constant” has historically evolved into the concepts of “dielectric function” and “dielectric permittivity” (references as far as in line 403!).

The authors have some strange mannerisms regarding the use of quotes. While in some places these seem reasonably used, I would recommend the authors to reconsider their use in general. More specific examples: l.10 ‘classic’, l.12 ‘crushing’, l. 118 ‘critical’, l. 147 ‘Mossotti catastrophe’, l. 230 ‘rarefication’, l. 233 ‘deep’, l. 234 ‘hidden’, l. 248 ‘window’, l. 263 ‘simple’. A more significant example is found in line 274: “which can be considered as the ’proof’ for the basic Arrhenius pattern” – it is not clear whether the authors want to put the proof in doubt, because the use of quotes can really convey suggestion of doubt.

The frequent use of italic font is also not typical. I consider it a part of the distinct style of the authors, making the manuscript more akin to a philosophical treatise than to a dry scientific report, but some readers can find it strange.

Line 383: „is shown” should be „as shown” or simply „shown”

End of reviewer remarks.

Author Response

1. Reviewer#1: ‘The authors do not provide detailed mechanistic insight into the observed anomaly, apart from the reference to a probable mechanism of “‘crushing’ crystalline grains by isotropic squeezing and increasing liquid layers between grains”. My question is: are there also more molecular explanations? Is it possible that some local reordering, molecular reorientation etc. takes place? Should such explanations be rather excluded and if so, why? The discussion around the line 492 of Conclusions should be enhanced to this effect.’
Answer: It is extremely difficult and requires further studies question. Notwithstanding based on this report and the results of earlier studies in nitrobenzene one can indicate the possible emergence of quasi-hexatic constraints induced liquid crystal–like fluids. This issue is extensively discussed in lines 517-575, in the given version of the report. It was associated with additional references/
2. Reviewer#1: ‘The discussion is in most parts very general. The numerical data (fitting to the equations) are provided in Figures 1, 2, 5 and 6, but not extensively discussed or compared with data for other compounds (if available). On the other hand, I cannot see the steepness index equation parameters. Please provide some comment on the possibility (or non-possibility) of extended discussion of the fitted parameters‘
Answer: The only available similar results are for dielectric constant in thymol and menthol (by the authors), and they are directly recalled. The practical lack of such ‘comparative’ data results from 2 facts the common belief that the premelting effect is weak, limited, and cannot be parameterized in a way similar to the continuous phase transition.
One of the basic results of the given report is showing that by using dielectric methods, supported by pressure, one obtains the dominant response from liquid-like layers separating solid grains. Despite the fact that they constitute, minor-minor part of the bulk sample. This fact is (and was) strongly stressed in the paper, as the significant result.
3. Reviewer#1: ‘ There are some hints at such discussion, e.g. line 438: “with values of critical exponents indicating the classical, mean-field type description”, and they should be somewhat enlarged.
Answer: Please note that this issue was (and still is) explicitly described at the beginning of Conclusions section.
4. Reviewer#1: ‘ Moreover, the role of Figures 7 and 8, together with associated data, is not clear. Do they really belong to Materials and Methods? Are they necessary only to show the purity of material, accuracy of measurements etc.? Maybe they should be placed in the Results section and discussed?
Answer: They the part of the Materials and Methods section because they show spectra with relevant features used in the Results section. Namely, they show explicitly the location of dielectric constant and the selected frequency, which is important because in dielectric studies often measurement for some selected frequency is carried out and the decisive statement ‘this is dielectric constant’ is only given, Here, we can see its meaning. Also, the modulus loss curve is shown, to present the meaning of the relaxation time and the loss curve peak. Note that following the suggestion of one of the Reviewers, the Methods section is now just after the Introduction section. Consequently, the numbers of figures are re-arranged. Former Figs. 7 and 8 and now Figs. 1 and 1.
5. Reviewer#1: ‘ The authors have some strange mannerisms regarding the use of quotes. While in some places these seem reasonably used, I would recommend the authors to reconsider their use in general. More specific examples: l.10 ‘classic’, l.12 ‘crushing’, l. 118 ‘critical’, l. 147 ‘Mossotti catastrophe’, l. 230 ‘rarefication’, l. 233 ‘deep’, l. 234 ‘hidden’, l. 248 ‘window’, l. 263 ‘simple’. A more significant example is found in line 274: “which can be considered as the ’proof’ for the basic Arrhenius pattern”…‘
Answer: We reduced using quotes to the necessary minimum.
6. Reviewer#1: ‘The frequent use of italic font is also not typical. I consider it a part of the distinct style of the authors, making the manuscript more akin to a philosophical treatise than to a dry scientific report, but some readers can find it strange.
Answer: We reduced using italics to the necessary minimum.
7. Reviewer#1: ‘Line 383: „is shown” should be „as shown” or simply „shown”
Answer: has been corrected.

Reviewer 2 Report

The presented article is an independent and holistic study. During the reading of the manuscript, the reviewer has no comments. I believe that the manuscript can be published in the Journal Crystals.

From a closer examination of the manuscript, I would like to make one remark. The numerical data (fitting to the equations) are provided in Figures 1, 2, 5 and 6, but not extensively discussed or compared with data for other compounds. Not possible to found the steepness index equation parameters.

Author Response

Reviewer#2: From a closer examination of the manuscript, I would like to make one remark. The numerical data (fitting to the equations) are provided in Figures 1, 2, 5, and 6, but are not extensively discussed or compared with data for other compounds. Not possible to find the steepness index equation parameters.
Answer: This issue was also raised by Reviewer#1. The response is very basic: there is (almost) no comparable data in other compounds regarding parameterization, particularly critical-like, in other compounds from the premelting effect. There are only recent results in menthol and thymol for dielectric constant (by the authors) and slightly earlier nonlinear dielectric effect measurements by Pochec et al in higher alcohols. They are (and were) explicitly recalled in the report. For the premelting effect in high-pressure studies, the only (qualitative) evidence is in the very recent report by the authors on liquid crystalline undecylcyanobiphenyl (11CB), without analysis. Hence, the report contains all available results. Note, that it is probably the first report indicating the unique significance of dielectric studies supported by pressure to test the effect dominantly from liquid-like layers, even though are a very minor part of the sample. This indication is a significant result of the report.
Regarding the steepness index, note please Eq. 13 and the captions related to Figures, with values of relevant parameters.

Reviewer 3 Report

The report presents giant and long-range pre-melting effects appearing in dielectric properties for temperature and pressure paths of studies for the compound nitrobenzene with an explicit, critical-like structure. The results and comments offered are satisfactory. However, the text need revisions in terms of interpretation and presentation of the results. With minor adjustments, the manuscript is acceptable for a publication. Please see the enclosed comment file.

Comments for author File: Comments.pdf

Author Response

1. Reviewer#3: The reviewer suggested changes of the organization to 1. Introduction, 2. Experimental, 3. Results and Discussion..
Answer. It has been changed following the suggestion.
2. Reviewer#3: ‘There are many parameters, but not all are well described
Answer: The report has been tested with respect to the definition of all parameters.
3. Reviewer#3: ‘I did not understand the sentence “The authors of in ref. [ ] noted….”
Answer: It has been corrected. It was a misprint.