A Computational Study of AlF3 and ACF Surfaces
Round 1
Reviewer 1 Report
In this contribution from Pandharkar et al., the results of a numerical
study of the AlF3 and AlF_{3-x}Cl_{x} surfaces are reported. For both
systems, ten different possible surfaces were considered and the
corresponding surface energies calculated. The theoretical method that was
used for the calculations is density functional theory. The goal of this
study is to determine the most plausible (at T=0 K) structure of the
surface by comparing the surface energies. For both systems the
(0110) surface has the lowest surface energy.
I found the results very interesting and the research seems to have been
conducted with care. The manuscript is well written and the results
presented in a rather clear way. I have no particular criticisms to make
concerning the results and their interpretations. For these reasons
I recommend publication of the manuscript in Inorganics. However, there
are a few minor details (listed below) that I would like the authors to
consider when preparing the final version of the manuscript.
a) The authors chose the PBE (or PBE-D3(BJ)) exchange-correlation
functional for the calculations. I think that citing a few papers to
justify this choice for surface calculations would be good.
b) It is not 100% clear which exchange-correlation functional was used
for the calculations presented in section 3. Towards the end of
section 2.4, it is stated "..., we can safely compute our slabs without
D3 corrections". However, in the legends of Table 1 and Figure 2,
it is indicated that the results are from PBE-D3(BJ). Thus, it is
confusing and should be made more clear which functional has been used.
c) Related to point b), the used functional is not mentioned in the
legend of Table 2.
d) For clarity, the legends of the tables and figure should indicate
for which system the results are. Furthermore, for ACF the value of
x (the content of Cl) should be also indicated.
e) Page 10, lines 261-263: A part of the sentence ("substitutions rather
than energetics") is unclear.
f) There are a couple of typos that I detected during the course of the
reading:
Page 1, line 2: "has been" -> "have been"
Page 2, line 53: "activity in" -> "activity is"
Page 7, line 184: "of (1122) surface" -> "(1122) surface"
Page 9, line 237: "closer the surface" -> "closer to the surface"
Page 10, line 269: "effected" -> "affected"
Author Response
We thank the reviewer for his/her comments, which have helped to improve the paper and clarify the details of our model. Our point by point response is given below.
RC – Reviewer comments
AC – Author’s comments
RC: a) The authors chose the PBE (or PBE-D3(BJ)) exchange-correlation
functional for the calculations. I think that citing a few papers to
justify this choice for surface calculations would be good.
AC: We added some papers as examples for the choice of PBE for these kind of calculation in ionic compounds and gave a sentence in chapter 2.3. "In various ionic compounds PBE yields resonable results."
RC: b) It is not 100% clear which exchange-correlation functional was used
for the calculations presented in section 3. Towards the end of
section 2.4, it is stated "..., we can safely compute our slabs without
D3 corrections". However, in the legends of Table 1 and Figure 2,
it is indicated that the results are from PBE-D3(BJ). Thus, it is
confusing and should be made more clear which functional has been used.
AC: We clarified this and changed the sentence to "However, due to the uniform decrease over all surface energies, the shape of the crystal is nearly not effected by the D3 correction. But the absolute numbers of the surface energies should be interpreted with care."
RC: c) Related to point b), the used functional is not mentioned in the
legend of Table 2.
AC: Done
RC:d) For clarity, the legends of the tables and figure should indicate
for which system the results are. Furthermore, for ACF the value of
x (the content of Cl) should be also indicated.
AC: We have clearified the legends and added the systems. A general x can not be supplied because only Cl substitutions occurs on the surface, the bulk is still alpha-AlF3.
RC:e) Page 10, lines 261-263: A part of the sentence ("substitutions rather
than energetics") is unclear.
AC: We clarified this and changed the sentence to "Surface energies are generally destabilized upon substitution of fluorine by chloride."
RC:f) There are a couple of typos that I detected during the course of the
reading:
Page 1, line 2: "has been" -> "have been"
Page 2, line 53: "activity in" -> "activity is"
Page 7, line 184: "of (1122) surface" -> "(1122) surface"
Page 9, line 237: "closer the surface" -> "closer to the surface"
Page 10, line 269: "effected" -> "affected"
AC: Done
Reviewer 2 Report
The paper reports a detailed theoretical investigation on AlF3 and chlorine doped AlF3 surfaces. The calculations are performed for different surface slabs by means of periodic boundary conditions. The work is well presented and discussed. Therefore, I recommend the publication of the manuscript in the Journal of Inorganic Chemistry. I have only a few comments listed below:
Regarding the use of D3 dispersion correction it is not clear for me why the authors did not use it always; then, they would not need the warning about the total energy of the surface calculation on the last paragraph of page 4.
There are a few minor corrections:
Page 6 – line 161 – replace the comma by a point after the word “rearrangement”
Page 8 - line 188 – add “,respectively” after 1.85 Å; line 210 - replace “an” by and.
Page 9 – Caption of Table 2 – place the CN acronym after coordination number (CN) and not after the word surface; line 232 add the letter “e” to get the word “diverse”.
Author Response
We thank the reviewer for his/her comments, which have helped to improve the paper and clarify the details of our model. Our point by point response is given below.
RC – Reviewer comments
AC – Author’s comments
RC: Regarding the use of D3 dispersion correction it is not clear for me why the authors did not use it always; then, they would not need the warning about the total energy of the surface calculation on the last paragraph of page 4.
AC: Also the second reviewer ask this question. We clarified this and changed the sentence to "However, due to the
uniform decrease over all surface energies, the shape of the crystal is
nearly not effected by the D3 correction. But the absolute numbers of
the surface energies should be interpreted with care." Additionally we give in each caption the functional used.
RC:
Page 6 – line 161 – replace the comma by a point after the word “rearrangement”
Page 8 - line 188 – add “,respectively” after 1.85 Å; line 210 - replace “an” by and.
Page 9 – Caption of Table 2 – place the CN acronym after coordination number (CN) and not after the word surface; line 232 add the letter “e” to get the word “diverse”.
AC: Done
Reviewer 3 Report
This manuscript reports on a theoretical modeling of the AlF3 and its doped with chloride analogue by means of DFT electronic structure calculations. The work has been professionally executed and the methods employed are more than adequate to serve the present purpose. The manuscript is comprehensive and very well written. The subject of the study is of potential interest to many researchers working in the fields of materials and catalysis. I strongly recommend publication of this nice work in Inorganics.
Author Response
We thank the reviewer for the careful reading and the benevolent answer.
