Chapter 48 Crystal structures and crystal chemistry of ternary rare earth-transition metal borides silicides and homologues

Parteé, E.; Chabot, B.

doi:10.1016/s0168-1273(84)06005-0

Cited by 56 publications

(44 citation statements)

References 217 publications

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“…[1][2][3] One large family within this huge number of intermetallics is represented by the equiatomic compounds RTX (R ) rare earth or actinoid, T ) transition metal, X ) element of the p block) with more than 1000 representatives. 1 They crystallize with about 40 different structure types.…”

Section: Introductionmentioning

confidence: 99%

Equiatomic Intermetallic Europium Compounds: Syntheses, Crystal Chemistry, Chemical Bonding, and Physical Properties

2000

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The crystal chemistry of ternary equiatomic europium compounds EuTX (T ) transition metal; X ) element of the III, IV, or V main group) is reviewed. Besides preparation techniques we have especially focused on the structure-property relationships and peculiarities in chemical bonding. A main interest in these compounds is the valence state of the europium atoms. The magnetic susceptibility and electrical conductivity data, 151 Eu Mössbauer spectroscopic results and L III X-ray absorption experiments are discussed in detail.

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Section: Introductionmentioning

confidence: 99%

Equiatomic Intermetallic Europium Compounds: Syntheses, Crystal Chemistry, Chemical Bonding, and Physical Properties

2000

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“…This corresponds to the Ca subfamily of the larger structure series R 2+n T 2 E 2+n (E = Si, Ge) that has been described for n = 1, 2, and 4 for a wide range of rare-earth metals (R) and with essentially Fe, Co, and Ni as transition metals (T). 26,27 Therefore, the structure of 3 is best described using the chemical twinning approach as the result of a topological fusion of fragments of CaMGe (TiNiSi-type with M = Mg/Ag) 11,28,29 and CaGe (CrB-type) 30 structures. The member with n = 3 was predicted to adopt the space group Cmcm, 5 with only seven atomic positions, Wyckoff sequence f 5 c 2 .…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Valence State Driven Site Preference in the Quaternary Compound Ca₅MgAgGe₅: An Electron-Deficient Phase with Optimized Bonding

et al. 2014

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The quaternary phase Ca 5 Mg 0.95 Ag 1.05(1) Ge 5 (3) was synthesized by high-temperature solid-state techniques, and its crystal structure was determined by single-crystal diffraction methods in the orthorhombic space group Pnma -Wyckoff sequence c 12 with a = 23.1481(4) Å, b = 4.4736(1) Å, c = 11.0128(2) Å, V = 1140.43(4) Å 3 , Z = 4. The crystal structure can be described as linear intergrowths of slabs cut from the CaGe (CrB-type) and the CaMGe (TiNiSi-type; M = Mg, Ag) structures. Hence, 3 is a hettotype of the hitherto missing n = 3 member of the structure series with the general formula R 2+n T 2 X 2+n , previously described with n = 1, 2, and 4. The member with n = 3 was predicted in the space group Cmcm -Wyckoff sequence f 5 c 2 . The experimental space group Pnma (in the nonstandard setting Pmcn) corresponds to a klassengleiche symmetry reduction of index two of the predicted space group Cmcm. This transition originates from the switching of one Ge and one Ag position in the TiNiSi-related slab, a process that triggers an uncoupling of each of the five 8f sites in Cmcm into two 4c sites in Pnma. The Mg/Ag site preference was investigated using VASP calculations and revealed a remarkable example of an intermetallic compound for which the electrostatic valency principle is a critical structure-directing force. The compound is deficient by one valence electron according to the Zintl concept, but LMTO electronic structure calculations indicate electronic stabilization and overall bonding optimization in the polyanionic network. Other stability factors beyond the Zintl concept that may account for the electronic stabilization are discussed. (3) was synthesized by high-temperature solid-state techniques, and its crystal structure was determined by single-crystal diffraction methods in the orthorhombic space group Pnma − Wyckoff sequence c 12 with a = 23.1481(4) Å, b = 4.4736(1) Å, c = 11.0128(2) Å, V = 1140.43(4) Å 3 , Z = 4. The crystal structure can be described as linear intergrowths of slabs cut from the CaGe (CrB-type) and the CaMGe (TiNiSi-type; M = Mg, Ag) structures. Hence, 3 is a hettotype of the hitherto missing n = 3 member of the structure series with the general formula R 2+n T 2 X 2+n , previously described with n = 1, 2, and 4. The member with n = 3 was predicted in the space group Cmcm − Wyckoff sequence f 5 c 2 . The experimental space group Pnma (in the nonstandard setting Pmcn) corresponds to a klassengleiche symmetry reduction of index two of the predicted space group Cmcm. This transition originates from the switching of one Ge and one Ag position in the TiNiSi-related slab, a process that triggers an uncoupling of each of the five 8f sites in Cmcm into two 4c sites in Pnma. The Mg/Ag site preference was investigated using VASP calculations and revealed a remarkable example of an intermetallic compound for which the electrostatic valency principle is a critical structure-directing force. The compound is deficient by one valence electron according to the Zintl concept, but LMTO ...

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“…Many of the crystal structures of this system are well-described in the literature [60,61], which reveals rich interrelationships among its structures. In the following sections, we will see how PRINCEPS uncovers these patterns interconnecting the phase diagram's seemingly chaotic scattering of phases, with minimal intervention on the part of the user.…”

Section: Analysis Of Crystal Structures In the Ce-ni-si Systemmentioning

confidence: 99%

PRINCEPS: A Computer-Based Approach to the Structural Description and Recognition of Trends within Structural Databases, and Its Application to the Ce-Ni-Si System

Guo

Fredrickson

2016

Crystals

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Abstract:Intermetallic crystal structures offer an enormous structural diversity, with an endless array of structural motifs whose connection to stability and physical properties are often mysterious. Making sense of the often complex crystal structures that arise here, developing a clear structural description, and identifying connections to other phases can be laborious and require an encyclopedic knowledge of structure types. In this Article, we present PRINCEPS, an algorithm based on a new coordination environment projection scheme that facilitates the structural analysis and comparison of such crystal structures. We demonstrate the potential of this approach by applying it to the complex Ce-Ni-Si ternary system, whose 17 binary and 21 ternary phases would present a daunting challenge to one seeking to understand the system by manual inspection (but has nonetheless been well-described through the heroic efforts of previous researchers). With the help of PRINCEPS, most of the ternary phases in this system can be rationalized as intergrowths of simple structural fragments, and grouped into a handful of structural series (with some outliers). These results illustrate how the PRINCEPS approach can be used to organize a vast collection of crystal structures into structurally meaningful families, and guide the description of complex atomic arrangements.

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Chapter 48 Crystal structures and crystal chemistry of ternary rare earth-transition metal borides silicides and homologues

Cited by 56 publications

References 217 publications

Equiatomic Intermetallic Europium Compounds: Syntheses, Crystal Chemistry, Chemical Bonding, and Physical Properties

Equiatomic Intermetallic Europium Compounds: Syntheses, Crystal Chemistry, Chemical Bonding, and Physical Properties

Valence State Driven Site Preference in the Quaternary Compound Ca₅MgAgGe₅: An Electron-Deficient Phase with Optimized Bonding

PRINCEPS: A Computer-Based Approach to the Structural Description and Recognition of Trends within Structural Databases, and Its Application to the Ce-Ni-Si System

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Chapter 48 Crystal structures and crystal chemistry of ternary rare earth-transition metal borides silicides and homologues

Cited by 56 publications

References 217 publications

Equiatomic Intermetallic Europium Compounds: Syntheses, Crystal Chemistry, Chemical Bonding, and Physical Properties

Equiatomic Intermetallic Europium Compounds: Syntheses, Crystal Chemistry, Chemical Bonding, and Physical Properties

Valence State Driven Site Preference in the Quaternary Compound Ca5MgAgGe5: An Electron-Deficient Phase with Optimized Bonding

PRINCEPS: A Computer-Based Approach to the Structural Description and Recognition of Trends within Structural Databases, and Its Application to the Ce-Ni-Si System

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Valence State Driven Site Preference in the Quaternary Compound Ca₅MgAgGe₅: An Electron-Deficient Phase with Optimized Bonding