Thermal Transport Properties of Na2X (X = O and S) Monolayers
Round 1
Reviewer 1 Report
The present study is a kind of simple standard analysis of materials using first principles calculations.
In Section 2, clearly mention the system size, with the number of atoms. Mention the system size dependence of the results. This is important for analyzing the transport phenomena. It gives the readers the criteria how the present study accurate or not.
Other minor comments:
In Line 141 and 167, “2” of “Na2S” should be subscript.
In Reference 32, some LaTeX commands still remain.
Author Response
We thank the reviewer for careful check and valuable suggestions.
(1) In Section 2, clearly mention the system size, with the number of atoms. Mention the system size dependence of the results. This is important for analyzing the transport phenomena. It gives the readers the criteria how the present study accurate or not.
We add the atom numbers in Section 2. The supercell is extended to 7×7×1 and contains 147 atoms in total. Please see Page 2 and Line 80.
(2) In Line 141 and 167, “2” of “Na2S” should be subscript.
The subscript problem has been checked in whole manuscript.
(3) In Reference 32, some LaTeX commands still remain.
We delete all LaTeX commands in Reference.
Reviewer 2 Report
The manuscript presents theoretical calculations of thermal conductivity of Na2X monolayers based on Density Functional Theory. This property is important, in particular for thermoelectric materials and the present results could be useful to the field. The authors use well known computational tools (Quantum Espresso, Phonopy, ShengBTE) to obtain their results. The manuscript is sufficiently well written, but some points must be addressed before publication:
- in the title it is stated that the investigated compounds are Na2X with X=O and Se. However, in several other points (text, figures) it is written Na2S not Na2Se. As S and Se are NOT the same, the authors must correct this all over the manuscript. To be frank, it makes the whole work appear rather sloppy...
- several methodogical points in the manuscript should be explained better, expecially for a readership of coatings which is not specialized in theoretical calculations. I suggest to expand the methodology section in order to address this issue. For example, it should be explained why third-order IFC are needed here and how exactly are they calculated. Another point, how are the Gruneisen parameters calculated? There are different types of Gruneisen parameters, which one are the authors refering to here? Also, the P3 parameter discussed at pag. 6 should be explained better.
- pag. 2, line 57-58, change "The generalized gradient approximation (GGA) of the Perdew-Burke-Ernzerhof (PBE) [24] pseudopotentials are utilized...." in "The generalized gradient approximation (GGA) of the Perdew-Burke-Ernzerhof (PBE) [24] funtional is utilized...."
- pag. 2, line 70, PHONOPY is mispelled
- pag. 5, line 121-122, is should be specified that the valued of thermal conductivity here are at RT
- pag. 5, line 126, the size of what?
- pag. 5, line 144, the authors cite previous results but it is not clear which ones. Add a proper reference.
- pag. 6, line 152, the symbol gamma is used here but nowhere it is said that it is the Gruneisen parameter
Author Response
We thank the reviewer for careful check and valuable suggestions.
(1)-in the title it is stated that the investigated compounds are Na2X with X=O and Se. However, in several other points (text, figures) it is written Na2S not Na2Se. As S and Se are NOT the same, the authors must correct this all over the manuscript. To be frank, it makes the whole work appear rather sloppy...
We are sorry about this stupid mistake. We exchange all “Se” by “S”.
(2) - several methodogical points in the manuscript should be explained better, expecially for a readership of coatings which is not specialized in theoretical calculations. I suggest to expand the methodology section in order to address this issue. For example, it should be explained why third-order IFC are needed here and how exactly are they calculated. Another point, how are the Gruneisen parameters calculated? There are different types of Gruneisen parameters, which one are the authors refering to here? Also, the P3 parameter discussed at pag. 6 should be explained better.
It is really a hard work to give a clear explanation of the calculation method. We try our best to explain some import parameters and add more references. Please see Page 2 and Lines 65-77.
(3)- pag. 2, line 57-58, change "The generalized gradient approximation (GGA) of the Perdew-Burke-Ernzerhof (PBE) [24] pseudopotentials are utilized...." in "The generalized gradient approximation (GGA) of the Perdew-Burke-Ernzerhof (PBE) [24] funtional is utilized...."
We changed the “pseudopotentials” by “funtional”. Please see Page 2 and Line 58.
(4) - pag. 2, line 70, PHONOPY is mispelled
We changed the “PHONONPY” by “PHONOPY”. Please see Page 2 and Line 80.
(5) - pag. 5, line 121-122, is should be specified that the valued of thermal conductivity here are at RT
We add the temperature in this sentence. Please see Page 5 and Line 131.
(6) - pag. 5, line 126, the size of what?
The word “size” means the size of the system. To avoid misleading readers, we describe this part in more details. Please see Page 5 and Lines 136-139.
(7) - pag. 5, line 144, the authors cite previous results but it is not clear which ones. Add a proper reference.
In this sentence, we want to describe that the trend of group velocity is different from the trend of thermal conductivity. To avoid misleading readers, we describe this part in more details. Please see Page 5 and Lines 155-156.
(8)- pag. 6, line 152, the symbol gamma is used here but nowhere it is said that it is the Gruneisen parameter
In the Section 2, we add the symbol gamma to represent the Gruneisen parameter. Please see Page 2 and Line 75.
