ChemInform Abstract: Ba8Cu16P30. ‐ A New Ternary Variant of the Clathrate I Type Structure.

Duenner, J.; Mewis, A.

doi:10.1002/chin.199524013

Cited by 3 publications

(3 citation statements)

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“…These results demonstrate that the type I clathrate phase, BaCu 2 P 3.75 , is the high temperature phase that is stable over a small temperature interval, whereas BaCu 2 P 4 is stable at lower temperatures. This is additionally supported by a previous report that the BaCu 2 P 3.75 clathrate cannot be synthesized from elements by annealing at 1073 K, with the formation of BaCu 2 P 4 observed instead . We have confirmed these findings; the cleanest samples of BaCu 2 P 4 were obtained by annealing the elements at 1100 K.…”

Section: Resultssupporting

confidence: 90%

“…The synthesis of BaCu 2 P 4 was hampered by the existence of the type I clathrate compound of a similar composition, Ba 8 Cu 16 P 30 = BaCu 2 P 3.75 . , 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 ).…”

Section: Resultsmentioning

confidence: 99%

“…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. − In this work, we discuss the synthesis, crystal structures, and properties of nickel and copper phosphide clathrates whose crystal structures feature polyhedra containing square faces.…”

Section: Introductionmentioning

confidence: 99%

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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: Resultssupporting

confidence: 90%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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Evolution of structure and transport properties of the Ba8Cu16P30 clathrate-I framework with the introduction of Ga

Sarkar

Viswanathan

Yox

et al. 2022

Applied Physics Letters

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Two type-I clathrates were synthesized by introducing Ga into the framework of the Ba8Cu16P30 type-I clathrate. The introduction of minute amounts of Ga, 1.9% Ga/ Mtotal (where Mtotal = Cu + Ga), resulted in the disturbance of the completely ordered Pbcn superstructure of Ba8Cu16P30. Ba8Cu15.43(2)Ga0.3P30.26(3) crystallizes in a partially ordered orthorhombic Pmna clathrate-I superstructure with five out of 15 framework sites being jointly occupied by metal+phosphorus. Increasing the Ga content resulted in all framework sites being occupied by metal + phosphorus in the archetype cubic Pm[Formula: see text] n clathrate-I crystal structure of Ba8Cu14.5(3)Ga1.3P30.2(4) with 8.2% Ga/ Mtotal. A combination of energy dispersive x-ray spectroscopy, inductively coupled plasma mass spectroscopy, and single crystal x-ray diffraction was used to determine the structures alongside the compositions. The positional disorder was verified by 31P solid state NMR spectroscopy. Characterization of the transport properties indicated that the Ga-substituted samples exhibit higher Seebeck coefficients and electrical resistivities compared to its pristine counterpart, in line with the expected reduction of the hole concentration due to Ga/Cu substitution. Moderate improvements in the thermoelectric power factor and overall figure-of-merit were observed for samples with 6.9% and 3.8% Ga/ Mtotal as compared to those for the pristine Ba8Cu16P30 clathrate. Band structure calculations shed light on how Ga substitution affects the electronic structure and thermoelectric properties of studied clathrates.

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Formation of clathrates

Rogl

2005

ICT 2005. 24th International Conference on Thermoelectrics, 2005.

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ChemInform Abstract: Ba8Cu16P30. ‐ A New Ternary Variant of the Clathrate I Type Structure.

Cited by 3 publications

References 1 publication

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)

Evolution of structure and transport properties of the Ba8Cu16P30 clathrate-I framework with the introduction of Ga

Formation of clathrates

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ChemInform Abstract: Ba8Cu16P30. ‐ A New Ternary Variant of the Clathrate I Type Structure.

Cited by 3 publications

References 1 publication

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)

Evolution of structure and transport properties of the Ba8Cu16P30 clathrate-I framework with the introduction of Ga

Formation of clathrates

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Product

Resources

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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)

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