#
Band Structure of Organic-Ion-Intercalated (EMIM)_{x}FeSe Superconductor

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## Abstract

**:**

## 1. Introduction

## 2. Computation Details and Crystal Structure

## 3. Results and Discussion

## 4. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 2.**Crystal structure of (EMIM)${}_{x}$FeSe. (

**a**,

**b**) plane view (

**c**) shows the EMIM arrangement within the layer. Unit cell is marked by a rectangle.

**Figure 3.**Charge density difference induced by the interaction between the FeSe and EMIM cations. Unit cell is marked by a rectangle. Dark teal and deep violet wireframe areas indicate electron-excess and electron-deficient regions, respectively. Isosurface level is $1.3\times {10}^{-3}$${{a}_{0}}^{-3}$, where ${a}_{0}$ is the Bohr radius.

**Figure 4.**Comparison of the DFT-calculated band structure (

**a**,

**c**) and top views of Fermi surfaces (

**b**,

**d**) of (EMIM)${}_{2}$Fe${}_{18}$Se${}_{18}$ (

**a**,

**b**) and of FeSe with the similar crystal structure (

**c**,

**d**). The Fermi level corresponds to zero in panels (

**a**,

**c**).

**Figure 5.**Perspective views of Fermi surfaces for (EMIM)${}_{2}$Fe${}_{18}$Se${}_{18}$ (

**a**) and FeSe with the similar crystal structure (

**b**).

**Figure 6.**DFT-calculated band structure of (EMIM)${}_{2}$Fe${}_{18}$Se${}_{18}$ where the orbital contributions of EMIM (

**a**), Fe-${d}_{{x}^{2}-{y}^{2}}$, Fe-${d}_{xz}$, Fe-${d}_{yz}$ (

**b**), Fe-${d}_{xy}$, Fe-${d}_{3{z}^{2}-{r}^{2}}$ (

**c**) are shown by circles with sizes proportional to the corresponding weights. For visual clarity, the sizes are multiplied by 0.02 for EMIM and by 0.014 for all Fe-d orbitals except for Fe-${d}_{yz}$ that is multiplied by 0.012. The Fermi level corresponds to zero.

**Figure 7.**Total density of states of (EMIM)${}_{2}$Fe${}_{18}$Se${}_{18}$ (TDOS, black solid curves) and partial density of states (PDOS) of Fe 3d orbitals (violet curves) and EMIM cations (blue curves). Artificial broadening is taken to be 0.05 eV. PDOS of EMIM cations in the vicinity of the Fermi level is shown in the inset. The Fermi level corresponds to zero.

**Figure 8.**Wannier-interpolated bands obtained from Fe-d states (green curves) of (EMIM)${}_{2}$Fe${}_{18}$Se${}_{18}$ and the original band structure (violet curves). Most of the interpolated bands overlap perfectly with the original bands. The Fermi level corresponds to zero.

**Table 1.**Structural parameters of two EMIM cations located in FeSe. The atomic numbering scheme is shown in Figure 1.

Bond Length, Å | |||||||
---|---|---|---|---|---|---|---|

N1–C2 | N1–C5 | N1–C7 | C2–N3 | N3–C4 | N3–C6 | C4–C5 | C7–C8 |

1.346 | 1.389 | 1.474 | 1.346 | 1.388 | 1.463 | 1.365 | 1.520 |

1.346 | 1.389 | 1.475 | 1.347 | 1.387 | 1.461 | 1.364 | 1.519 |

Bond Angles in Degrees | |||||||

N1–C2–N3 | C2–N3–C4 | N3–C4–C5 | C2–N3–C6 | C4–C5–N1 | C2–N1–C5 | C2–N1–C7 | N1–C7–C8 |

108.11 | 108.82 | 107.18 | 125.16 | 106.92 | 108.96 | 125.56 | 112.12 |

108.01 | 108.88 | 107.21 | 125.61 | 106.92 | 108.97 | 125.40 | 111.96 |

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**MDPI and ACS Style**

Begunovich, L.V.; Korshunov, M.M.
Band Structure of Organic-Ion-Intercalated (EMIM)_{x}FeSe Superconductor. *Materials* **2022**, *15*, 1856.
https://doi.org/10.3390/ma15051856

**AMA Style**

Begunovich LV, Korshunov MM.
Band Structure of Organic-Ion-Intercalated (EMIM)_{x}FeSe Superconductor. *Materials*. 2022; 15(5):1856.
https://doi.org/10.3390/ma15051856

**Chicago/Turabian Style**

Begunovich, Lyudmila V., and Maxim M. Korshunov.
2022. "Band Structure of Organic-Ion-Intercalated (EMIM)_{x}FeSe Superconductor" *Materials* 15, no. 5: 1856.
https://doi.org/10.3390/ma15051856