Role of Surface Effects in the Vibrational Density of States and the Vibrational Entropy in Spin Crossover Nanomaterials: A Molecular Dynamics Investigation
Round 1
Reviewer 1 Report
This is an excellent addition to further understand the evolution of spin transition propeties at the nanoscale. This complex, multi-variable problem is highly complex and difficult, but the authors are able to reach interesting conclusions well-matching experimental observations.
The article is well written, and well articulated, and it will certainly be of high interest to the readers of magnetochemistry. No revisions ae needed in my opinion.
Author Response
We thank the referee 1 for his consideration.
Reviewer 2 Report
Alaa Fahs et al. used the so-called slab method to investigate surface vibrational and associated thermodynamical properties of nanoscale SCO films. They revealed the role of surface effects in the vibrational density of states and the vibrational entropy in spin crossover nanomaterials. This is worth publishing.
They consider the octahedra constituted of iron surrounded by six nitrogen atoms. And Me-L is 2.0 A for LS, 2.1A for HS, and L-L is 1.0A. By using this simplified structure, they write "below a thickness of 12 nm" in the abstract. In the real crystal, what kind of meaning does this value have?
Figure 4: If we compare a) and c), b) and c), the value from LS at 21 nm and the value from HS at 8 nm are missing. Please check it.
Author Response
We thank the referee 2 for his consideration.
Regarding the referee comments:
- They consider the octahedra constituted of iron surrounded by six nitrogen atoms. And Me-L is 2.0 A for LS, 2.1A for HS, and L-L is 1.0A. By using this simplified structure, they write "below a thickness of 12 nm" in the abstract. In the real crystal, what kind of meaning does this value have?
Answer: Such ultrathin crystalline films of SCO materials have already been synthesized and characterized for their SCO properties and revealed interesting size reduction effects (see for example references 9, 13 and 14 in the manuscript). As such, we feel their theoretical investigation is highly relevant.
Figure 4: If we compare a) and c), b) and c), the value from LS at 21 nm and the value from HS at 8 nm are missing. Please check it.
Answer: We thank the referee for the careful reading. The reason for the two missing points in Fig. 4c is that the calculated entropy values were negative (within the error bars) and therefore they were omitted. However, when checking this figure, we have realized there was a point with erroneous poistion, which is now corrected in the revised MS.
Reviewer 3 Report
This is manuscript presents computational work that aims to characterize dynamical properties of spin-crossover materials. In particular, the authors utilize molecular dynamics simulations to study the vibrational density of stated (and properties derived from it) of thin film. Overall, it is a nicely written manuscript with interesting results. Although somewhat specific, the combination of the analysis of the materials and the assessment of the computational technique makes it worth publishing. I offer a few comments that can help to improve the manuscript:
- Perhaps some small assessment of the force filed for some experimental observable, or some higher-level calculation such as DFT could help.
- Figure 4 should have the y axis a tad bigger.
Author Response
We thank the referee for considering our paper.
Regarding the referee comments:
1. Perhaps some small assessment of the force filed for some experimental observable, or some higher-level calculation such as DFT could help.
Answer: The key experimental observable for which the force field was assessed is the sound velocity and metal-ligand stretching frequencies of SCO materials (obtained from nuclear inelasting scattering measurements) and their spin state dependence (see page 5). That said, we agree with the referee that DFT calculations and MD simulations on real compounds, instead of the simplified 'model compound' of the present MS, will be an important perspective for our work.
Figure 4 should have the y axis a tad bigger.
Answer: We put a revised figure 4 into the MS (including also changes vs. the remark of referee 2).
