An official website of the United States government
Abstract A new ternary lithium zinc germanide, Li13.83Zn1.17(2)Ge4, was synthesized by a high‐temperature solid state reaction of the respective elements. The crystal structure was determined by single‐crystal X‐ray diffraction methods. The new phase crystallizes in the body‐centered cubic space groupI3d(no. 220) with unit cell parameter of 10.695(1) Å. The crystal structure refinements show that the parent Li15Ge4structure is stabilized as Li15−xZnxGe4(x≈1) via random substitution of Li atoms by the one‐electron‐richer atoms of the element Zn, by virtue of which the number of valence electrons increases, leading to a more electronically stable system. The substitution effects in the parent Li15Ge4structure were investigated through both theory and experiment, which confirm that the Zn atoms in this structure prefer to occupy only one of the two available crystallographic sites for Li. The preferred substitution pattern established from experimental results is supported by DFT electronic structure calculations, which also explore the subtleties of the chemical bonding and the electronic properties of the title compounds.
more »
« less
Lithium metal atoms fill vacancies in the germanium network of a type-I clathrate: synthesis and structural characterization of Ba 8 Li 5 Ge 41
Clathrate phases with crystal structures exhibiting complex disorder have been the subject of many prior studies. Here we report syntheses, crystal and electronic structure, and chemical bonding analysis of a Li-substituted Ge-based clathrate phase with the refined chemical formula Ba8Li5.0(1)Ge41.0, which is a rare example of ternary clathrate-I where alkali metal atoms substitute framework Ge atoms. Two different synthesis methods to grow single crystals of the new clathrate phase are presented, in addition to the classical approach towards polycrystalline materials by combining pure elements in desired stoichiometric ratios. Structure elucidations for samples from different batches were carried out by single-crystal and powder X-ray diffraction methods. The ternary Ba8Li5.0(1)Ge41.0 phase crystallizes in the cubic type-I clathrate structure (space group no. 223, a 10.80 Å), with the unit cell being substantially larger compared to the binary phase Ba8Ge43 (Ba8□3Ge43, a 10.63 Å). The expansion of the unit cell is the result of the Li atoms filling vacancies and substituting atoms in the Ge framework, with Li and Ge co-occupying one crystallographic (6c) site. As such, the Li atoms are situated in four-fold coordination environment surrounded by equidistant Ge atoms. Analysis of chemical bonding applying the electron density/ electron localizability approach reveals ionic interaction of barium with the Li–Ge framework, while the lithium-germanium bonds are strongly polar covalent.
more »
« less
- Award ID(s):
- 2004579
- PAR ID:
- 10498885
- Publisher / Repository:
- Dalton Transactions
- Date Published:
- Journal Name:
- Dalton Transactions
- Volume:
- 52
- Issue:
- 30
- ISSN:
- 1477-9226
- Page Range / eLocation ID:
- 10310 to 10322
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Several Ba−Li−Ge ternary phases are known and structurally characterized, including the title compound Ba2LiGe3. Its structure is reported to contain [Ge6]10−anions that exhibit delocalized bonding with a Hückel‐like aromatic character. The Ge atoms are in the same plane with the Li atoms, and if both types of atoms are considered as covalently bonded, [LiGe3]4−honeycomb‐like layers will result. The latter are separated by slabs of Ba2+cations. However, based on the systematic work detailed herein, it is necessary to re‐evaluate the phase as Ba2Li1−xGe3+x(x<0.05). Although small, the homogeneity range is clearly demonstrated in the gradual change of the unit cell for four independent samples. Subsequent characterization by single‐crystal X‐ray diffraction methods shows that the Ba2Li1−xGe3+xstructure, responds to the varied number of valence electrons and the changes are most pronounced for the refined lengths of the Li−Ge and Ge−Ge bonds. Indirectly, the changes in the Ge−Li/Ge distances within layers affect the stacking too, and these changes can be correlated to the variation of thec‐cell parameter. Chemical bonding analysis based on TB‐LMTO‐ASA level calculations affirms the notion for covalent character of the Ge−Ge bonds; the Ba−Ge and Li−Ge interactions also show some degree of covalency.more » « less
-
A new ternary phase has been synthesized and structurally characterized. BaLi x Cd 13– x ( x ≈ 2) adopts the cubic NaZn 13 structure type (space group Fm 3 ¯ c , Pearson symbol cF 112) with unit cell parameter a = 13.5548 (10) Å. Structure refinements from single-crystal X-ray diffraction data demonstrate that the Li atoms are exclusively found at the centers of the Cd 12 -icosahedra. Since a cubic BaCd 13 phase does not exist, and the tetragonal BaCd 11 is the most Cd-rich phase in the Ba–Cd system, BaLi x Cd 13– x ( x ≈ 2) has to be considered as a true ternary compound. As opposed to the typical electron count of ca. 27 e -per formula unit for many known compounds with the NaZn 13 structure type, BaLi x Cd 13– x ( x ≈ 2) only has ca. 26 e -, suggesting that both electronic and geometric factors are at play. Finally, the bonding characteristics of the cubic BaLi x Cd 13– x ( x ≈ 2) and tetragonal BaCd 11 are investigated using the TB-LMTO-ASA method, showing metallic-like behavior.more » « less
-
Reported is the synthesis of a new polar intermetallic phase, Ca4CdIn2Ge4, crystals of which can be readily obtained employing the In‐flux method. The structure and the chemical composition of the new compound are established based on single‐crystal X‐Ray diffraction and energy‐dispersive X‐Ray spectroscopy data. Ca4CdIn2Ge4crystallizes in a monoclinic crystal system with the space groupC2/m(no. 12) with lattice parametersa = 16.7383(12) Å,b = 4.4235(3) Å,c = 7.4322(5) Å, andβ = 106.560(1)°. The structure can formally be classified as a variant of the Mg5Si6structure type (Pearson symbolmS22). Considering the InGe and CdGe interactions as mostly covalent, the polyanionic substructure can be rationalized as consisting of ribbons of edge‐shared [InGe4] tetrahedra connected by Ge2dimers and bridged by Cd atoms in nearly square‐planar environment. Chemical bonding analysis based on TB‐LMTO‐ASA calculations affirms the notion for covalent character of the GeGe bonding with the dimers. The calculations also show that the bonding in the tetrahedra is more covalent in character than the bonding in square‐planar fragments, with the CaGe interactions being the least covalent among all interactions, though not exactly ionic.more » « less
-
Single crystals of a new ternary chalcogenide Cu3InSe4 were obtained by induction melting, allowing for a complete investigation of the crystal structure by employing high-resolution single-crystal synchrotron X-ray diffraction. Cu3InSe4 crystallizes in a cubic structure, space group P4¯3m, with lattice constant 5.7504(2) Å and a density of 5.426 g/cm3. There are three unique crystallographic sites in the unit cell, with each cation bonded to four Se atoms in a tetrahedral geometry. Electron localization function calculations were employed in investigating the chemical bonding nature and first-principle electronic structure calculations are also presented. The results are discussed in light of the ongoing interest in exploring the structural and electronic properties of new chalcogenide materials.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D3DT01168B
