#
Charge Ordering Transitions of the New Organic Conductors δ_{m}- and δ_{o}-(BEDT-TTF)_{2}TaF_{6}

^{1}

^{2}

^{3}

^{4}

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## Abstract

**:**

## 1. Introduction

## 2. Results

## 3. Discussion

## 4. Materials and Methods

## 5. Conclusions

## Supplementary Files

Supplementary File 1## Acknowledgments

## Author Contributions

## Conflicts of Interest

## References

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**Figure 1.**Crystal structure of ${\mathsf{\delta}}_{m}$-(BEDT-TTF)${}_{2}$TaF${}_{6}$ (

**a**) and the ${\mathsf{\delta}}_{o}$ phase (

**b**) projected approximately along the molecular short axis. The donor layer of the ${\mathsf{\delta}}_{m}$ phase (

**c**) and the ${\mathsf{\delta}}_{o}$ phase (

**d**) projected approximately along the molecular long axis. The energy band structure and the Fermi surface of the ${\mathsf{\delta}}_{m}$ phase (

**e**) and the ${\mathsf{\delta}}_{o}$ phase (

**f**).

**Figure 2.**Temperature dependence of the resistivity of the ${\mathsf{\delta}}_{m}$ phase (

**a**) and the ${\mathsf{\delta}}_{o}$ phase (

**b**). The insets show the Arrhenius plots, and solid lines in the insets are fits to the data.

**Figure 3.**Temperature dependence of Seebeck coefficients of the ${\mathsf{\delta}}_{m}$ and ${\mathsf{\delta}}_{o}$ phases.

**Figure 4.**Temperature dependence of ESR g-values (

**a**), linewidths (

**b**), and the relative spin susceptibilities (

**c**) of the ${\mathsf{\delta}}_{m}$ and ${\mathsf{\delta}}_{o}$ phases. The applied magnetic field is perpendicular to the conducting layer for both compounds. The inset shows the Arrhenius plots, and solid lines in the inset are fits to the data.

**Figure 5.**X-ray oscillation photographs of the ${\mathsf{\delta}}_{m}$ phase at 298 K (

**a**) and 171 K (

**b**), and of the ${\mathsf{\delta}}_{o}$ phase at 309 K (

**c**) and 171 K (

**d**).

**Figure 6.**Temperature dependence of the integrated intensity of superlattice reflections. The background intensities are subtracted. Although integrated intensity is measured using a four circle diffractometer for the ${\mathsf{\delta}}_{o}$ phase, this is measured using an imaging plate for the ${\mathsf{\delta}}_{m}$ phase. The indices of the used reflections are $4,-1/2,-3$ for the ${\mathsf{\delta}}_{m}$ phase, and $8,-3/2,-1/2$ for the ${\mathsf{\delta}}_{o}$ phase.

**Figure 7.**Crystal structure of the ${\mathsf{\delta}}_{m}$ phase at 171 K (

**a**,

**b**) and of the ${\mathsf{\delta}}_{o}$ phase at 39 K (

**c**,

**d**). Four crystallographically independent molecules (A, B, C, and D) exist for both phases (

**a**,

**c**). A and C (B and D) molecules are flat (bent). Black rounded rectangles denote hole-rich molecules, and ${t}_{q}$ is the interaction mode q in the high temperature structure (

**b**,

**d**).

**Figure 8.**Anion volume dependence of the charge ordering temperature of $\mathsf{\delta}$-type (BEDT-TTF)${}_{2}M$F${}_{6}$ ($M=$ P, As, Sb, and Ta). Anion volumes are estimated using Figure 2 in Ref. [14]. Dashed lines are guides to the eye.

**Figure 9.**Charge order patterns of the $\mathsf{\delta}$-type salts. (

**a**) uniform; (

**b**) horizontal stripe; (

**c**) vertical stripe; and (

**d**) checkerboard. The dashed line shows a unit cell.

**Figure 10.**Charge ordering temperatures as a function of $|{t}_{q}|$. The dashed line shows linear dependence.

${\mathsf{\delta}}_{\mathit{m}}$ Phase | ${\mathsf{\delta}}_{\mathit{o}}$ Phase | |||
---|---|---|---|---|

Formula | C${}_{20}$H${}_{16}$S${}_{16}$TaF${}_{6}$ | |||

Formula weight | $1064.24$ | |||

Temperature (K) | 298 | 171 | 298 | 39 |

Crystal system | Monoclinic | Monoclinic | Orthorhombic | Monoclinic |

Space group | $C2/c$ | $P{2}_{1}/n$ | $Pnna$ | $P2/c$ |

a (Å) | $35.825\left(12\right)$ | $35.6108\left(6\right)$ | $14.924\left(9\right)$ | $13.2594\left(5\right)$ |

b (Å) | $6.679\left(4\right)$ | $13.2887\left(2\right)$ | $33.366\left(14\right)$ | $14.5036\left(4\right)$ |

c (Å) | $14.953\left(8\right)$ | $14.7148\left(3\right)$ | $6.656\left(2\right)$ | $33.8724\left(7\right)$ |

$\mathsf{\beta}$ (deg) | $110.62\left(3\right)$ | $110.1387\left(8\right)$ | – | $101.206\left(2\right)$ |

V (Å${}^{3}$) | $3349\left(3\right)$ | $6537.7\left(2\right)$ | $3315\left(3\right)$ | $6389.8\left(3\right)$ |

Z | 4 | 8 | 4 | 8 |

Total reflections | 4877 | 11899 | 2921 | 27208 |

Reflections [${F}^{2}>2\mathsf{\sigma}\left({F}^{2}\right)$] | 3571 | 7889 | 1558 | 20909 |

$R1$ [${F}^{2}>2\mathsf{\sigma}\left({F}^{2}\right)$] | $0.0327$ | $0.0818$ | $0.0748$ | $0.1387$ |

$wR2$ (all reflections) | $0.0944$ | $0.2172$ | $0.2498$ | $0.3242$ |

GOF | $1.028$ | $1.128$ | $1.026$ | $1.231$ |

**Table 2.**Transfer integrals and geometrical parameters of the $\mathsf{\delta}$-type (BEDT-TTF)${}_{2}$TaF${}_{6}$ salts.

Interaction Mode | t (meV) | R (Å) | $\mathsf{\omega}$ (deg) |
---|---|---|---|

${\mathsf{\delta}}_{m}$ phase | |||

c | $-75.6$ | $6.68$ | |

$a1$ | $-103.3$ | $4.49$ | $29.9$ |

$a2$ | $38.4$ | $4.18$ | |

p | $-23.8$ | $8.05$ | |

q | $-147.8$ | $5.72$ | |

${\mathsf{\delta}}_{o}$ phase | |||

c | $-79.4$ | $6.66$ | |

$a1$ | $-95.9$ | $4.51$ | $29.9$ |

$a2$ | $37.1$ | $4.19$ | |

p | $-24.5$ | $8.04$ | |

q | $-141.2$ | $5.72$ |

${\mathsf{\delta}}_{\mathit{m}}$-PF${}_{\mathbf{6}}$ | ${\mathsf{\delta}}_{\mathit{o}}$-PF${}_{\mathbf{6}}$ | ${\mathsf{\delta}}_{\mathit{m}}$-AsF${}_{\mathbf{6}}$ | ${\mathsf{\delta}}_{\mathit{o}}$-AsF${}_{\mathbf{6}}$ | ${\mathsf{\delta}}_{\mathit{m}}$-SbF${}_{\mathbf{6}}$ | ${\mathsf{\delta}}_{\mathit{o}}$-SbF${}_{\mathbf{6}}$ | ${\mathsf{\delta}}_{\mathit{m}}$-TaF${}_{\mathbf{6}}$ | ${\mathsf{\delta}}_{\mathit{o}}$-TaF${}_{\mathbf{6}}$ | |
---|---|---|---|---|---|---|---|---|

existence | ${}^{b}$ | yes | yes | yes | yes | ${}^{b}$ | yes | yes |

spin singlet | – | yes | yes | yes | yes | – | yes | yes |

superlattice ${}^{a}$ | – | ${\mathit{c}}^{*}/2$ | ${\mathit{b}}^{*}/2$ | ${\mathit{c}}^{*}/2$ | ${}^{b}$ | – | ${\mathit{b}}^{*}/2$ | ${\mathit{b}}^{*}/2+{\mathit{c}}^{*}/2$ |

charge ordering | – | yes | yes | yes | yes | – | yes | yes |

${T}_{c}$ (K) | – | 297 | 264 | $\sim 298\phantom{\rule{3.33333pt}{0ex}}{}^{c}$ | 273 | – | 276 | 300 |

Ref. | – | [1,6,8,9] | [4,5,13] | [6,8] | [4,13] | – | ${}^{d}$ | ${}^{d}$ |

**Table 4.**Transfer integrals and geometrical parameters of the $\mathsf{\delta}$-type (BEDT-TTF)${}_{2}$AsF${}_{6}$ and (BEDT-TTF)${}_{2}$PF${}_{6}$ salts.

Interaction Mode | t (meV) | R (Å) | $\mathsf{\omega}$ (deg) |
---|---|---|---|

${\mathsf{\delta}}_{m}$-AsF${}_{6}$ ${}^{a}$ | |||

c | $-77.7$ | $6.67$ | |

$a1$ | $-109.5$ | $4.45$ | $29.9$ |

$a2$ | $33.2$ | $4.14$ | |

p | $-23.4$ | $8.01$ | |

q | $-156.4$ | $5.71$ | |

${\mathsf{\delta}}_{o}$-AsF${}_{6}$ ${}^{b}$ | |||

c | $-74.8$ | $6.69$ | |

$a1$ | $-98.4$ | $4.50$ | $30.1$ |

$a2$ | $32.3$ | $4.20$ | |

p | $-22.4$ | $8.07$ | |

q | $-139.5$ | $5.76$ | |

${\mathsf{\delta}}_{o}$-PF${}_{6}$ (From Ref. [2]) | |||

c | $-84$ | – | |

$a1$ | $-104$ | – | – |

$a2$ | 32 | – | |

p | $-28$ | – | |

q | $-141$ | – |

**Table 5.**Potential energies of the charge-ordered patterns per unit cell in the $\mathsf{\delta}$-type.

Pattern | V Energy | ${\mathit{V}}_{\mathit{a}}$ Energy |
---|---|---|

Uniform | ${E}_{u}=\frac{U}{4}+{V}_{a}+{V}_{c}+{V}_{p}+\frac{{V}_{q}}{2}$ | $\frac{U}{4}+2.57{V}_{a}$ |

Horizontal | ${E}_{h}=\frac{U}{2}+2{V}_{c}$ | $\frac{U}{2}+1.3{V}_{a}$ |

Vertical | ${E}_{v}=\frac{U}{2}+2{V}_{a}$ | $\frac{U}{2}+2{V}_{a}$ |

Checkerboard | ${E}_{c}=\frac{U}{2}+2{V}_{p}+{V}_{q}$ | $\frac{U}{2}+1.84{V}_{a}$ |

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## Share and Cite

**MDPI and ACS Style**

Kawamoto, T.; Kurata, K.; Mori, T.; Kumai, R.
Charge Ordering Transitions of the New Organic Conductors δ* _{m}*- and δ

*-(BEDT-TTF)*

_{o}_{2}TaF

_{6}.

*Magnetochemistry*

**2017**,

*3*, 14. https://doi.org/10.3390/magnetochemistry3010014

**AMA Style**

Kawamoto T, Kurata K, Mori T, Kumai R.
Charge Ordering Transitions of the New Organic Conductors δ* _{m}*- and δ

*-(BEDT-TTF)*

_{o}_{2}TaF

_{6}.

*Magnetochemistry*. 2017; 3(1):14. https://doi.org/10.3390/magnetochemistry3010014

**Chicago/Turabian Style**

Kawamoto, Tadashi, Kohei Kurata, Takehiko Mori, and Reiji Kumai.
2017. "Charge Ordering Transitions of the New Organic Conductors δ* _{m}*- and δ

*-(BEDT-TTF)*

_{o}_{2}TaF

_{6}"

*Magnetochemistry*3, no. 1: 14. https://doi.org/10.3390/magnetochemistry3010014