Introducing a Magnetic Guest to a Tetrel-Free Clathrate: Synthesis, Structure, and Properties of EuxBa8–xCu16P30 (0 ≤ x ≤ 1.5)

Kovnir, Kirill; Stockert, U.; Budnyk, S.; Prots, Yurii; Baitinger, Michael; Paschen, S.; Shevelkov, Аndrei V.; Grin, Yuri

doi:10.1021/ic201474h

Cited by 55 publications

(42 citation statements)

References 51 publications

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“…Upon heating, two endothermic peaks at 1107(5) and 1139(5) K were observed. The second endothermic peak temperature is close to the melting temperature of the BaCu 2 P 3.75 clathrate-I, 1134 K. 9 We hypothesize that the first peak, which has a significantly lower (7) intensity, corresponds to the phase transformation BaCu 2 P 4 → BaCu 2 P 3.75 + 0.25P. Several annealing experiments were carried out to verify this hypothesis ( Figure S2 in the Supporting Information).…”

Section: ■ Introductionmentioning

confidence: 76%

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Twisted Kelvin Cells and Truncated Octahedral Cages in the Crystal Structures of Unconventional Clathrates, AM₂P₄ (A = Sr, Ba; M = Cu, Ni)

et al. 2015

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A new strontium nickel polyphosphide, SrNi 2 P 4 , was synthesized from elements and structurally characterized by single-crystal X-ray diffraction. It crystallizes in the orthorhombic space group Fddd (No. 70), with Z = 8. The crystal structure is that of a clathrate type, composed of Ni 8 P 16 , 14-faced polyhedral cages that encapsulate Sr atoms. Together with the previously reported but unrecognized clathrate VII, BaNi 2 P 4 , and another previously reported clathrate, BaCu 2 P 4 , which is isostructural to SrNi 2 P 4 , a family of transition metal−phosphorus clathrates is represented. The crystal structures of each of the discussed transition metal-based clathrates are composed of unique polyhedra containing square faces. These structural fragments were predicted to be unstable for the conventional clathrates based on Si, Ge, and Sn. In this work, we report the crystal and electronic structures, chemical bonding, as well as the thermoelectric properties of this novel class of unconventional clathrates. ■ INTRODUCTIONGas hydrates, also known as clathrates, are a fascinating class of compounds with a crystal structure composed of a tetrahedral water framework encapsulating guest atoms and molecules inside large polyhedral cages. 1 Inorganic clathrates have similar crystal structures, comprised of covalently bound tetrahedral frameworks of heavier elements. 2−4 The frameworks of the majority of inorganic clathrates are formed from group 14 elements, Si, Ge, or Sn, which are known as tetrels. Guest cations or anions can be encapsulated inside those cages (Figure 1 top), providing atomic vibrations that are essentially independent of the surrounding framework, making clathrates promising thermoelectric materials.Inorganic clathrates crystallize into six structure types, which can be described as a tiling of space using several types of polyhedra. For known tetrel clathrates, the polyhedra are composed of pentagonal and hexagonal faces (Figure 1 top). 2−4 The crystal structure of the most common type I clathrate is composed of pentagonal dodecahedra and tetrakaidecahedra (Figures 1a, b).The stability of known and hypothetical tetrel clathrates was scrutinized by means of theoretical calculations, which predicted the lowest stability for clathrate structure types composed mainly of tetrel atoms with local coordinations that deviate furthest from a regular tetrahedral coordination. 6 The highest distortion of this local coordination occurs for tetrel elements occupying vertices of the square faces of polyhedral cages. It was proposed that clathrates formed by polyhedra with square faces should be unstable, and indeed, no such tetrel clathrates have been reported. [2][3][4]6 The energy landscape and stability of clathrates can be significantly modified by diverging from tetrel elements. Several groups have recently shown that type I clathrate frameworks can be formed from a combination of late transition metals, Zn, Cd, Cu, and Au, along with a pnicogen, a group 15 element: P, As, or Sb. 7−11 In this work, we discuss...

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Section: ■ Introductionmentioning

confidence: 76%

“…8,9 Slow crystallization of the melt or annealing of a sample with the nominal composition BaCu 2 P 4 resulted primarily in the formation of BaCu 2 P 3.75 . A detailed DSC investigation revealed that BaCu 2 P 4 is a low-temperature phase, which transforms to the clathrate-I, BaCu 2 P 3.75 , at high temperatures ( Figure 2).…”

Section: ■ Introductionmentioning

confidence: 99%

Twisted Kelvin Cells and Truncated Octahedral Cages in the Crystal Structures of Unconventional Clathrates, AM₂P₄ (A = Sr, Ba; M = Cu, Ni)

et al. 2015

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“…Fig. 6 shows a plot of C v /T 3 versus T 2 , which reveals a broad maximum at around 12.5 K. From this maximum, a value of Â E = 63 K is obtained considering that an Einstein contribution shows up in this type of plot as a maximum at 0.2Â E , whereas the Debye contribution is constant at low temperatures [36,38]. It is noticeable that the obtained Â E is the same as the one calculated from the crystal data for the equatorial motion of the I2 atom.…”

Section: Atomic Displacement and Characteristic Temperaturesmentioning

confidence: 99%

Low-temperature structure and lattice dynamics of the thermoelectric clathrate Sn24P19.3I8

Новиков

Matovnikov

Avdashchenko

et al. 2012

Journal of Alloys and Compounds

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“…Polyphosphides are known to form a variety of crystal structures with different elements [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. From three-dimensional frameworks to isolated cages, phosphorous backbones form a wide range of stable structures.…”

Section: Introductionmentioning

confidence: 99%

Zintl Salts Ba2P7X (X = Cl, Br, and I): Synthesis, Crystal, and Electronic Structures

Dolyniuk

Kovnir

2013

Crystals

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Two barium phosphide halides, Ba 2 P 7 Br and Ba 2 P 7 I, were synthesized and structurally characterized by single crystal X-ray diffraction. Both compounds crystallize in the monoclinic space group P2 1 /m (No. 11) and are isostructural to Ba 2 P 7 Cl. The crystal structures of Ba 2 P 7 X (X = Cl, Br, I) feature the presence of heptaphosphanortricyclane P 7 3− clusters along with halogen anions and barium cations. According to the Zintl concept, Ba 2 P 7 X compounds are electron-balanced semiconductors. Quantum-chemical calculations together with UV-Visible spectroscopy confirm the title compounds are wide bandgap semiconductors. The bonding in the P 7 3− clusters was analyzed by means of electron localization function. The elemental compositions were confirmed using energy dispersive X-ray spectroscopy.

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Introducing a Magnetic Guest to a Tetrel-Free Clathrate: Synthesis, Structure, and Properties of Eu_xBa_8–xCu₁₆P₃₀ (0 ≤ x ≤ 1.5)

Cited by 55 publications

References 51 publications

Twisted Kelvin Cells and Truncated Octahedral Cages in the Crystal Structures of Unconventional Clathrates, AM₂P₄ (A = Sr, Ba; M = Cu, Ni)

Twisted Kelvin Cells and Truncated Octahedral Cages in the Crystal Structures of Unconventional Clathrates, AM₂P₄ (A = Sr, Ba; M = Cu, Ni)

Low-temperature structure and lattice dynamics of the thermoelectric clathrate Sn24P19.3I8

Zintl Salts Ba2P7X (X = Cl, Br, and I): Synthesis, Crystal, and Electronic Structures

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Introducing a Magnetic Guest to a Tetrel-Free Clathrate: Synthesis, Structure, and Properties of EuxBa8–xCu16P30 (0 ≤ x ≤ 1.5)

Cited by 55 publications

References 51 publications

Twisted Kelvin Cells and Truncated Octahedral Cages in the Crystal Structures of Unconventional Clathrates, AM2P4 (A = Sr, Ba; M = Cu, Ni)

Twisted Kelvin Cells and Truncated Octahedral Cages in the Crystal Structures of Unconventional Clathrates, AM2P4 (A = Sr, Ba; M = Cu, Ni)

Low-temperature structure and lattice dynamics of the thermoelectric clathrate Sn24P19.3I8

Zintl Salts Ba2P7X (X = Cl, Br, and I): Synthesis, Crystal, and Electronic Structures

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Introducing a Magnetic Guest to a Tetrel-Free Clathrate: Synthesis, Structure, and Properties of Eu_xBa_8–xCu₁₆P₃₀ (0 ≤ x ≤ 1.5)

Twisted Kelvin Cells and Truncated Octahedral Cages in the Crystal Structures of Unconventional Clathrates, AM₂P₄ (A = Sr, Ba; M = Cu, Ni)

Twisted Kelvin Cells and Truncated Octahedral Cages in the Crystal Structures of Unconventional Clathrates, AM₂P₄ (A = Sr, Ba; M = Cu, Ni)