Systematic Investigation on Surface Diradicals Using Theoretical Models: 2M/MgO and 2M/BaO (M = Cu, Ag, and Au)
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe manuscript systematically employed the AP-DFT/plane-wave method to study the adsorption behavior of bimetallic systems with diradical characteristics on oxide surfaces, revealing the mechanism by which surface adsorption regulates diradical features. The study yielded many intriguing results, with a clear structure, in-depth analysis, and significant academic value. The manuscript is suitable for publication.
Comments: The methods section could be streamlined to make the main focus of the manuscript, particularly in the sections describing the AP-DFT method.
Author Response
The manuscript systematically employed the AP-DFT/plane-wave method to study the adsorption behavior of bimetallic systems with diradical characteristics on oxide surfaces, revealing the mechanism by which surface adsorption regulates diradical features. The study yielded many intriguing results, with a clear structure, in-depth analysis, and significant academic value. The manuscript is suitable for publication.
Comments: The methods section could be streamlined to make the main focus of the manuscript, particularly in the sections describing the AP-DFT method.
Response: Thank you for your evaluation of our paper. We have revised the methods section to make it more readable and to focus on the AP-DFT method.
Author Response File: Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe review is attached.
Comments for author File: Comments.pdf
Author Response
In this study Tada et al. explore the interaction between adsorbed diradicals/diradicaloids onto MgO/BaO surfaces. In order to describe the systems theoretically, they used the approximate spin projected density functional theory with plane-wave basis (AP-DFT/plane-wave). In addition, they verified the accuracy of the AP-DFT/plane-wave method against the QD-NEVPT2 method, which takes into account the static correlation effects, which are of primary importance for diradicals and diradicaloids. The paper is well written and organized. Also, it represents a timely analysis of compounds and electronic effects of significant importance. Last but not least, the topic of the paper is in unison with the works of Prof. Nakano, who devoted his academic career to the relationship between open-shell character of the compounds and material properties.
Response: Thank you for indicating not only the novelty of this paper, but also the significance of its publication in the Prof. Nakano memorial issue. The comments were fruitful, and we have performed additional calculations and discussions based on the comments to improve the quality of our study.
Minor suggestions for improvement:
- The spacing between the equations is limited and this hampers the reading of the paper.
- Equation number (8) is not complete, they are missing indices in the formula.
Therefore, I recommend careful editing of the paper before the resubmission.
Response: We have corrected the points you mentioned, read the paper again, and revised the typos. For Eq.(8), we have removed it as it was a redundant part (see responses to comments in the referees 1 and 3).
Specific questions to the authors:
- On Page 6 the authors wrote: “The active space is two orbitals with two electrons, and the initial guesses for the CAS calculations are summarised in Supporting Information (Figure S1).” This means that only the static correlation associated with the s-electrons of the metal atoms is taken into account. However, for d-elements there is a term called double-d-shell effect (https://pubs.acs.org/doi/10.1021/ct300211j). Did the authors tried to explore larger active space and to include d-type orbitals in the multi-configurational calculations?
Response: Thank you for your very interesting suggestion. We have performed CAS calculation of 12 orbitals with 22 electrons to confirm the effect of d orbitals. As a result, no obvious effect of the additional d orbitals on the diradical character, which is the main target of our study, could be detected. The models of the present study is dominated by the contribution from the s orbitals, and the AP-DFT method is fine for qualitative discussions.
Although described as the QD-NEVPT2 method in previous manuscripts, CAS calculations for the ground state per each spin state are sufficient to obtain the results of our study; hence, QD correction is not significant. The word, QD-NEVPT2, have been corrected to NEVPT2 or CASSCF.
- On Page 10, Table 3 the authors represent results for the diradical characters of the Xgas M models obtained with the AP-DFT/plane-wave and the QD-NEVPT2 methods. Although, I do not expect quantitative agreement between both methods in some cases the differences are significant. In particular, for models Bgas-2M (M=Au, Ag or Cu). At the DFT level these systems are closed shell, while they are predicted as diradicaloids with the multi-configurational approach. The authors gave a reasonable explanation of this disagreement. However, I would like to asked them to explore another hypothesis. As well known, sometimes the convergence of the broken symmetry solution (for example with the UNO method) is not straightforward, especially when dealing with highly symmetric systems as M……M. In these cases, during calculations the symmetry should be off and the more difficult ones require also wave function stability check and optimization. I would like to ask the author if they are sure that the nearly zero diradical character for models Bgas-2M is not due to some convergence problems? I will highly appreciate if the answers of the author are adequately supported by computational results.
Based on the above comments, I recommend major revision of the manuscript.
Response: As the referee pointed out, it is difficult to obtain BS results presented in this study when using symmetry options. For reproducibility, we have stated in the methods section that symmetry was not used. Even if symmetry is off, a symmetry may be acquired during the SCF cycle and converge to an unexpected symmetric state. Hence, the SCF process and converged states were carefully checked to avoid convergence to such erroneous solutions. The absence of convergence to artificial closed-shell structures is also confirmed by the continuous nature of the plots of T against interatomic distances shown in Fig. S2. However, in the previous manuscript, Fig. S2 was cited only for another discussion. We have stated that the results in Fig. S2 clearly confirm the closed-shell solution of the Bgas-2M system is not an SCF problem.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsPaper by Kohei Tada et al titled “ Systematic investigation on surface diradicals using theoretical models: 2M/MgO and 2M/BaO (M = Cu, Ag, and Au)”
The main aim of paper is to study theoretically the effect of interaction of diradicals immobilized on the surface of MgO and BaO. The motivation of paper is the potential application of diradicals for material applications. This paper is based on approaches previously developed by the authors and on the advanced method of quantum chemical calculation.
Paper is written in very consequent manner and describes in details all needed formular, confirmed by appropriate analysis. It is written very clear and contain a few misprints only.
Formular 8 has some unclear terms. Probably because of some problems of my computer.
The main result of paper made on the base of computation is the different effect of the surface on the diradical character for Au and Ag. For Au the diradical character is increased by the orbital polarization of MnO and BaO while for Ag the diradical character is decreased due to donation of electron from surface.
This is nice very accurately written paper. No doubt it will be interesting for readers of Chemistry and should be recommended as it is.
Author Response
The main aim of paper is to study theoretically the effect of interaction of diradicals immobilized on the surface of MgO and BaO. The motivation of paper is the potential application of diradicals for material applications. This paper is based on approaches previously developed by the authors and on the advanced method of quantum chemical calculation.
Paper is written in very consequent manner and describes in details all needed formular, confirmed by appropriate analysis. It is written very clear and contain a few misprints only.
Formular 8 has some unclear terms. Probably because of some problems of my computer.
The main result of paper made on the base of computation is the different effect of the surface on the diradical character for Au and Ag. For Au the diradical character is increased by the orbital polarization of MnO and BaO while for Ag the diradical character is decreased due to donation of electron from surface.
This is nice very accurately written paper. No doubt it will be interesting for readers of Chemistry and should be recommended as it is.
Response: Thank you for your high evaluation of our paper and kind comments. Eq. (8) in the previous manuscript was deleted for readability because the sentence immediately following “The exact all-electron wavefunction is an eigenfunction of the spin operator, but is not due to the contamination of higher-order spin states.” was the same meaning.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsIn its present form the paper is suitable for publication in the MDPI-Chemistry journal.