Study of the Bandgap and Crystal Structure of Cu4TiSe4: Theory vs. Experiment
, Szymon Sutuła 2, Paweł Jóźwik 3, Krzysztof Krawczyk 1 and Krzysztof Woźniak 2
Round 1
Reviewer 1 Report
This work performs single crystals of tetracopper tetraselenotitanate, Cu4TiSe4, using solid-state synthesis. Technically, the authors employ experimental and simulation methods with apparent authority. This manuscript is well written, and the results are interesting for the readers. However, the following points should be addressed before accepting this manuscript (with minor revision.
1. The computation setting using Uspex algorithm should be clarified in more detail. If possible, can you mathematically describe the Uspex algorithm in the text (or in the supplementary doc)?
2. Please clarify why you chose the Uspex algorithm to calculate the band gap of the crystal structure. There are many methods to calculate the band gap structure, e.g., PWE, FEM, and FDTD. To benefit for the readers to know the other popular approaches for band gap calculations, e.g., the plane wave expansion (PWE) method (see Optics Express, 2011, 19, 4862–4867), the related literature is suggested to include in the reference.
3. The reference cited in the introduction should be improved. For example, the related references with respect to lines 29-32 and lines 32-35 should be quoted in the text.
Author Response
Ad. 1. We have added more description of Uspex algorithm to the manuscript. We also point reader to the Uspex manual where he can find a detailed description of its action.
Ad. 2. We have added appropriate clarification to the text.
Ad. 3. We have added corresponding quotations to the indicated areas.
Reviewer 2 Report
The authors have provided a brief study but I have concern which should be addressed before acceptance.
1. More additional experimental study should be included in this manuscript.
2. Thermal stability phonon calculations for presented crystals must be considered.
3. Compare experimental absorption with simulated absorption.
4. Consider electron localization function to understand the binding mechanism.
5. Whether these structure are dynamically stable?
Author Response
Ad. 1. We have included all experimental studies that we have conducted in the text. In our opinion, they are sufficient to support our conclusions.
Ad. 2. The thermal stability lies outside of our research goal. Also such calculations were performed previously.
Ad. 3. We have already compared the values of theoretical and experimental optical bandgaps.
Ad. 4. Thank You for proposition. However, the binding mechanism is not of interest in this manuscript.
Ad. 5. These structures were obtained experimentally and are stable.
