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Article
Peer-Review Record

Spontaneous and Piezo Polarization Versus Polar Surfaces: Fundamentals and Ab Initio Calculations

Materials 2025, 18(7), 1489; https://doi.org/10.3390/ma18071489
by Pawel Strak 1,*, Pawel Kempisty 1,2, Konrad Sakowski 1,3, Jacek Piechota 1, Izabella Grzegory 1, Eva Monroy 4, Agata Kaminska 1,5,6 and Stanislaw Krukowski 1,*
Reviewer 1:
Reviewer 2: Anonymous
Reviewer 3: Anonymous
Materials 2025, 18(7), 1489; https://doi.org/10.3390/ma18071489
Submission received: 5 March 2025 / Revised: 20 March 2025 / Accepted: 21 March 2025 / Published: 26 March 2025

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This paper addresses the critical issue of defining spontaneous polarization in infinite solids. The authors validate their model using ab initio calculations on wurtzite and zinc blende III-nitrides, comparing results with Berry phase and superlattice methods. However, revisions to improve the quality are essential for broader acceptance.

  1. Clarify why HSE was used for spontaneous polarization calculations but PBE for zinc blende superlattices.
  2. The piezoelectric parameters in Table 3 show significant variation from literature. Please clarify this.
  3. The paper mentions computational constraints but does not quantify their impact. A discussion on how finer grids or larger supercells might alter results would strengthen conclusions.
  4. The Figures should be presented by a more clear format and correct units (like A should be corrected).

Author Response

Reviewer #1

 

Referee criticism

Clarify why HSE was used for spontaneous polarization calculations but PBE for zinc blende superlattices.

 

Our response

This is our error in writing. In fact HSE was calculated at final stage. We corrected the manuscript, i.e. abstract. In Fig. 10 for ZB we have PBE and HSE data.

_____________

 

Referee criticism

The piezoelectric parameters in Table 3 show significant variation from literature. Please clarify this.

 

Our response

In fact variation of these parameters may be related to the fact that we are limited to dense grid in one directions and lower density grid in other. But this is the limit of our computational possibilities.

_____________

 

Referee criticism

The paper mentions computational constraints but does not quantify their impact. A discussion on how finer grids or larger supercells might alter results would strengthen conclusions.

 

Our response

Generally this error is relatively small for spontaneous polarization as these are separated components. As mentioned above in the case of coupling between different piezo components via Poisson effect this may be larger because in the perpendicular the number of points is small.

_____________

 

Referee criticism

The Figures should be presented by a more clear format and correct units (like A should be corrected).

 

Our response

We apologize for that. It is corrected in the new version. The Figures were also improved.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors


The authors present the Polarization spontaneous/piezo and polar surfaces: fundamentals and their implementation in ab initio calculations. The research idea is well conceived. However, the research design needs some attention, and the manuscript needs some polish before publication. Though I have given more than eight comments, all the comments are minor. I would like to accept the paper after minor revision of the following remarks. 

1- The overall English is okay, but some sentences sometimes have structural issues. I want the authors to double-check for typos and structural English mistakes.

2- It would be better for the authors and the readers if the manuscript follows the proper MDPI materials' manuscript template to divide the paper into sections and subsections. The present layout is a bit confusing. 

3- Some figures are disbursed on multiple pages. Always align them on a single page.

4- Figure 4 colours are very dull, which tends to miss some information. I recommend using dark and bright colours for better visibility. Also, it would be difficult to understand Figure 4 in the grey version of the manuscript.

5- Provide the novelty statement in the abstract and the last introduction paragraph.

6-  Provide the bibliographic reference of the underlying base equations.

7- Figure 13 is not visible because of bad colouring choice.

8- The conclusion should be changed and written as per MDPI guidelines. Also, provide the limitations of this study and future directions to the conclusion section.

Comments on the Quality of English Language

Yes, minor issues

Author Response

Reviewer #2

 

1- The overall English is okay, but some sentences sometimes have structural issues. I want the authors to double-check for typos and  structural English mistakes.

 

Our response

We apologize for that. We corrected some sentences and carried out the language check.

_____________

 

Referee criticism

2- It would be better for the authors and the readers if the manuscript follows the proper MDPI materials' manuscript template to divide the paper into sections and subsections. The present layout is a bit confusing.

 

Our response

This paper contains important section describing new model. Therefore it is slightly different. As it is crucial we prefer to keep it that way. There are not other differences.

_____________

 

Referee criticism

3- Some figures are disbursed on multiple pages. Always align them on a single page.

 

Our response

We apologize for that. We corrected them accordingly.

_____________

 

Referee criticism

4- Figure 4 colours are very dull, which tends to miss some information. I recommend using dark and bright colours for better visibility. Also, it would be difficult to understand Figure 4 in the grey version of the  manuscript.

 

Our response

We apologize for that. We corrected it accordingly.

_____________

 

Referee criticism

5- Provide the novelty statement in the abstract and the last introduction paragraph.

 

Our response

The summary and conclusion Section (5) is actually great novelty statement because it presents

  • The state of art before publication
  • The results in the paper
  • The state of art after publication.

From these points it is clear what is the contribution of the manuscript and how important that is. We suggest that this form should be applied in any published paper. That would avoid redundant papers.

_____________

 

Referee criticism

6-  Provide the bibliographic reference of the underlying base equations.

 

Our response

Some references are added.

_____________

 

Referee criticism

7- Figure 13 is not visible because of bad colouring choice.

 

Our response

We apologize for that. We corrected it accordingly.

_____________

 

Referee criticism

8- The conclusion should be changed and written as per MDPI guidelines.  Also, provide the limitations of this study and future directions to the conclusion section.

Our response

The conclusions are written in new style. This is to prove that the paper (i) provides new results, (ii) they change the general scientific picture of the field. The limitations  and future directions are added to conclusion Section.

Finally we would like to thank all Referees for their extensive corrections that has helped us to improve the manuscript considerably.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript employs an original approach to address the polarization spontaneous/piezo and polar surfaces: fundamentals and their implementation in ab initio calculations. The authors also account for and develop the local model of spontaneous polarization and employ it to calculate spontaneous polarization. Besides the credit of developing an excellent and convincing model, much needed for the wurtzite nitride superlattice compounds, the authors put their model and comprehensive results in the right perspective and context, both method-wise and in relation to the class of materials. The discussion and the study as presented invokes notable insights into the realm of electronic/optical properties of group IIIA. The work presents new developments and brings new knowledge to the field. Conclusions are motivated and easy to perceive.
There are some minor queries/suggestions related to this excellent manuscript that need to be addressed before its publication, i.e., I recommend it for publication after a minor revision: 
1: Title: The phrase “polarization spontaneous/piezo and polar surfaces” is not optimal -both grammatically and logically. It is not stylistically appropriate for a title. Besides, the title could be shortened.
2: The DFT level of theory (basically, the HSE exchange-correlation functional) should be mentioned in the abstract
3: Lattice parameters/bond lengths obtained in DFT calculations are usually considered meaningful up till the third digit after the decimal point. It is not necessary (and usually considered not credible to operate, state, and compare results that include the forth digit after the decimal point).
4: Fig. 11: graph lines are too thin for comfortable reading.
5: Have the authors tested the impact of different unit cell size(s) on the accuracy of the calculation results?
6: The authors have already mentioned some studies of the electronic/optical properties of group IIIA nitrides at DFT level of theory but fail to comment/include some very recent comparative studies of group IIIA nitrides at ab initio levels which also extend to mesoscopic scale using the phase field model. (e.g., MAM Filho, et al., Crystal Growth & Design 24 (11), 4717-4727 (2024), and also RR Pela, et al. Physical Chemistry Chemical Physics 26 (9), 7504-7514 (2024)) which should be acknowledged in the Introduction.
7: Some long sentences, misspellings, etc., still are noticeable throughout the text. 

Author Response

Reviewer #3

Referee criticism

1: Title: The phrase “polarization spontaneous/piezo and polar surfaces” is not optimal -both grammatically and logically. It is not stylistically appropriate for a title. Besides, the title could be shortened.

 

Our response

The title was changed. It is shorter now

_____________

 

 

Referee criticism

2: The DFT level of theory (basically, the HSE exchange-correlation functional) should be mentioned in the abstract

Our response

Thank you for the comment. It is added now.

_____________

 

Referee criticism

3: Lattice parameters/bond lengths obtained in DFT calculations are usually considered meaningful up till the third digit after the decimal point. It is not necessary (and usually considered not credible to operate, state, and compare results that include the forth digit after the decimal point).

Our response

The custom in the x-ray is to use four digits. In the case of ab initio the precision is lower. We have kept four digits in the experimental data and three in ab initio.

_____________

 

Referee criticism

4: Fig. 11: graph lines are too thin for comfortable reading.

Our response

We apologize for the error. It is corrected now.

_____________

 

Referee criticism

5: Have the authors tested the impact of different unit cell size(s) on the accuracy of the calculation results?

Our response

No, we have used smallest single size calculation cell. Larger cells would cause more serious problems with the computational limitations.

_____________

 

Referee criticism

6: The authors have already mentioned some studies of the electronic/optical properties of group IIIA nitrides at DFT level of theory but fail to comment/include some very recent comparative studies of group IIIA nitrides at ab initio levels which also extend to mesoscopic scale using the phase field model. (e.g., MAM Filho, et al., Crystal Growth & Design 24 (11), 4717-4727 (2024), and also RR Pela, et al. Physical Chemistry Chemical Physics 26 (9), 7504-7514 (2024)) which should be acknowledged in the Introduction.

Our response

We thank the Referee for these recent publications. These are excellent papers. But they consider nanorods which are much above the calculation sizes used in our paper. So we cannot refer them in the context of our results.

_____________

 

Referee criticism

7: Some long sentences, misspellings, etc., still are noticeable throughout the text.

 

Our response

We apologize for that we corrected the manuscript linguistically. The changes are marked by  blue color.

_____________

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

All my concerns have been addressed, and the present form can be considered published.

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