Effect of Vacancy Defects and Hydroxyl on the Adsorption of Glycine on Mg(0001): A First-Principles Study
Round 1
Reviewer 1 Report
Article review
The article has been carefully analyzed.
The article is written in obscure scientific language and contains the following remarks.
1. In the abstract, it is necessary to show the need to solve the problem related to the adsorption of glycine on Mg(0001).
• What is meant by the sentence “…adsorption of Gly on a stepped surface area of Mg(0001)…”?
• How is “…concentration of surface vacancies-defects 1/3…” formed?
• How is “…increased charge transfer between adsorbent and surface…” defined?.
• Only the Mg(0001) surface has been studied. Therefore, the proposal should also be carefully edited: "The results of the calculations provide insight into the mechanism of interaction of biomolecules with surfaces of magnesium and magnesium-based alloys, and also point to some directions for future experimental efforts."
2. In the introduction you need to justify
• Why was glycine adsorption chosen specifically on the Mg(0001) surface?
• Mg has other surfaces, such as (1010 and 1011). Why is the Mg(0001) surface important?
• Analyzing [1-21] in one sentence justify the choice of the studied surface Mg(0001).
• Analyzing [22-31] in one sentence, justify also the adsorption of Gly on the metal surface.
• You need to write the purpose of the work. Specify the problem and, in accordance with this, write a specific goal. In other words: write why you need to conduct such a study?
• Why use the effect of vacancy defects and hydroxyl (OH) groups?
• Justify the choice of concentration of surface vacancy defects (1/36, 1/6, 1/3 and 1/2) and hydroxyl.
• The answer to the question how can: "The results of the calculations provide a better understanding of the reactivity of the surface of crystals with Mg and hydroxyl defects during the Gly adsorption process."
3. Computational methods
• The sentence "two layers of Mg atoms were fixed throughout the optimization" is repeated.
• Specify the essence of the method optB86b-vdW [41] in one sentence. Why should you use this particular method?
• Why was the thickness of the six-atom layer chosen?
• You must specify the accuracy of the calculation of Eads (eV).
3. Results and discussion
3.1. Adsorption of Gly on Mg(0001) Surfaces with Different Defect Concentrations
• On the basis of what are these four concentration vacancy defects 1/36, 1/6, 1/3 and 1/2 selected?
• It is not clear what the authors mean in the sentence (“…dative N-Mg and O-Mg covalent bond form stronger interactions)? Specify.
• For Gly adsorption on Mg(0001) surfaces with different defect concentrations, give a table similar to TABLE I (section 3.2)
3.2. Effect of hydroxyl on the adsorption of Gly on the Mg(0001) surface
• Table 1 should include data from [45] for comparison.
• This sentence is poorly written: “The calculated Eads of Gly on the Mg(0001) surface containing the hydroxyl is -1.11 eV, which is 0.05 eV less than the adsorption energy of Gly on the defect-free Mg(0001) surface (- 1.16 eV) [45].” Needs to be edited. In addition, instead of the word "less", it should be "more."
• Clarify the sentence “…close to the theoretical bond lengths for covalent bond formation [44]”.
3.3. Electronic Properties of Gly on Various Mg(0001) Surfaces
• Once again, in other words for the reader's understanding, to clarify what is meant by the words “…favorable adsorption structure of Gly in the stepped region?”.
• Clarify the words “…for the respective orbitals?”
• Clarify the sentence “…N1-Mg, O1-Mg and O2-Mg bond lengths are close to the theoretical N/O and Mg bond lengths to form a covalent bond”.
4. Conclusions
• Conclusions should be carefully edited to show the importance and novelty of the findings.
1. Give numerical values and show the importance of the data: "...affinities?", "Adsorbed in a stepped region?", "What is the most stable configuration?" specify.
2. Clarify "... four adsorption sites", what is the reason that "... part of the electrons is transferred from the surface of Mg (0001) to hydroxyl"?
3. Edit conclusion 3. Remove sentence: "The results show that amino acids have a wide range of potential applications in biological coating of material surfaces."
• At the end, give a brief summary and the essence of the reasons why this topic is important for research and what is new (whether expressed qualitatively or quantitatively) is proposed by the authors.
Consideration of these remarks is necessary for readers in order to clearly understand the novelty and importance of the results.
After correcting these remarks, the article can be recommended for publication.
It is necessary to write short sentences that are logically connected.
Remove unfounded words from the text.
Correct unclear sentences and remove repetitions.
Comments are in the review.
Author Response
We are very thankful to the reviewer for their in-depth review. We have revised our present research paper based on their valuable suggestions and comments. We hope our revision has improved the manuscript to their satisfaction. The answers to their specific comments/suggestions/queries are as follows.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript titled " Effect of Vacancy Defects and Hydroxyl on the Adsorption of Glycine on the Mg(0001): A First-principles Study" discusses the effect of vacancy defects and hydroxyl on the adsorption behavior of Glycine (Gly) on Mg(0001) surfaces. The novelty statement of the manuscript is excellent. The study collectively presents the results for Gly adsorption and states that the best adsorption occurs at the step region of Mg(0001) surface with a surface vacancy defect concentration of 1/3 due to the increased charge transfer between the adsorbent and the surface. Also, it states that the hydroxyl adsorbed at the FCC-hollow site is the most favorable adsorption site among the four adsorption locations. The manuscript is inline with the journal Coatings. Further, the study will remarkably be helpful in the field of mechanical, chemical, physical, and environmental engineering. The reviewer recommends publication of the manuscript in its present state.
Author Response
We are very thankful to the reviewer for their in-depth review. We have revised our present research paper based on their valuable suggestions and comments. We hope our revision has improved the manuscript to their satisfaction. The answers to their specific comments/suggestions/queries are as follows.
Author Response File: Author Response.pdf
Reviewer 3 Report
This manuscript nicely described the effect of vacancy defects and hydroxyl on the adsorption of glycine on the Mg(0001) through a theoretical study. The research is interesting and can be acceptable for the publication after minor revisions following the comments below.
C1. Novelty of the works should be more clearly focused for easy understanding of readers.
C2. Hydroxylated Mg(0001) surface seems negatively affect the adsorption of the glycine compare to the defected Mg(0001). Does author have any suggestion/investigation how hydroxylation of Mg(0001) surface can be restricted to get defect enriched Mg(0001) surface?
C3. Hydroxyl sometimes favor the adsorption through non-covalent/H-bonding interaction Please explain the possibility of such interactions.
C4. References should be updated via replacing good/recent ones in addition with formatting the reference style to follow author guide. Sometimes style are different, especially in titles!
Typical grammatical errors and typos should be checked and revised carefully!
Author Response
We are very thankful to the reviewer for their in-depth review. We have revised our present research paper based on their valuable suggestions and comments. We hope our revision has improved the manuscript to their satisfaction. The answers to their specific comments/suggestions/queries are as follows.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The corrected article has been carefully reviewed again.
The reviewer's comments have been largely taken into account and corrected.
The article is recommended for publication.
