Structure and Bonding of an Intergrowth Phase Ca7Ag2+xGe7-x (x approximate to 2/3) Featuring a Zintl-Type Polyanionic Chain
(2016) In European Journal of Inorganic Chemistry p.169-176- Abstract
- Single crystals of a new ternary phase, Ca7Ag2+xGe7-x [x = 0.48(3)], were obtained from as side-product of high-temperature solid-state reactions, and its crystal structure determined by X-ray diffraction methods. Following the Zintl concept, the anionic substructure consists of a novel pentameric Zintl anion [Ge-5](12-) with C-2v local symmetry, as well as [AgxGe2-x]((6-3x)-) units accounting for [Ge-2](6-) dimers and isolated Ge4- (and Ag+) species sharing the same atomic sites. DFT-level band structure calculations were carried out on a hypothetical, fully ordered model (x = 0). We found that the electronic structure associated with the planar W-shaped [Ge-5](12-) polyanions is more suited to optimize the structure's stability than the... (More)
- Single crystals of a new ternary phase, Ca7Ag2+xGe7-x [x = 0.48(3)], were obtained from as side-product of high-temperature solid-state reactions, and its crystal structure determined by X-ray diffraction methods. Following the Zintl concept, the anionic substructure consists of a novel pentameric Zintl anion [Ge-5](12-) with C-2v local symmetry, as well as [AgxGe2-x]((6-3x)-) units accounting for [Ge-2](6-) dimers and isolated Ge4- (and Ag+) species sharing the same atomic sites. DFT-level band structure calculations were carried out on a hypothetical, fully ordered model (x = 0). We found that the electronic structure associated with the planar W-shaped [Ge-5](12-) polyanions is more suited to optimize the structure's stability than the helical configuration of the isoelectronic [Se-5](2-), in the context of incomplete charge transfer from the electropositive metal Ca. Thus, the antibonding states at the Fermi level that are centered on the two [Ge-n]((2n+2)-) oligomers can be depopulated by means of Ge-to-Ca electron back donation, strengthening at the same time the Ge-Ge bonds. These antibonding states also endow the system with substantial electronic flexibility, which may result in some phase width. Finally, plausible local ordering models of Ag/Ge mixing in [AgxGe2-x]((6-3x)-) units for x = 2/3, as expected from the Zintl concept, are briefly discussed within the coloring problem approach. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/8747947
- author
- Ponou, Simeon LU ; Doverbratt, Isa LU ; Lidin, Sven LU and Miller, Gordon J.
- organization
- publishing date
- 2016
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- Zintl phases, Intermetallic compounds, Germanium, Electronic structure, Coloring problem
- in
- European Journal of Inorganic Chemistry
- issue
- 1
- pages
- 169 - 176
- publisher
- John Wiley & Sons Inc.
- external identifiers
-
- wos:000367727600021
- scopus:84953835383
- ISSN
- 1099-0682
- DOI
- 10.1002/ejic.201501176
- language
- English
- LU publication?
- yes
- id
- bb61ad3d-923b-4fca-afa8-c694fbd3304f (old id 8747947)
- date added to LUP
- 2016-04-01 10:04:24
- date last changed
- 2022-01-25 19:23:13
@article{bb61ad3d-923b-4fca-afa8-c694fbd3304f,
abstract = {{Single crystals of a new ternary phase, Ca7Ag2+xGe7-x [x = 0.48(3)], were obtained from as side-product of high-temperature solid-state reactions, and its crystal structure determined by X-ray diffraction methods. Following the Zintl concept, the anionic substructure consists of a novel pentameric Zintl anion [Ge-5](12-) with C-2v local symmetry, as well as [AgxGe2-x]((6-3x)-) units accounting for [Ge-2](6-) dimers and isolated Ge4- (and Ag+) species sharing the same atomic sites. DFT-level band structure calculations were carried out on a hypothetical, fully ordered model (x = 0). We found that the electronic structure associated with the planar W-shaped [Ge-5](12-) polyanions is more suited to optimize the structure's stability than the helical configuration of the isoelectronic [Se-5](2-), in the context of incomplete charge transfer from the electropositive metal Ca. Thus, the antibonding states at the Fermi level that are centered on the two [Ge-n]((2n+2)-) oligomers can be depopulated by means of Ge-to-Ca electron back donation, strengthening at the same time the Ge-Ge bonds. These antibonding states also endow the system with substantial electronic flexibility, which may result in some phase width. Finally, plausible local ordering models of Ag/Ge mixing in [AgxGe2-x]((6-3x)-) units for x = 2/3, as expected from the Zintl concept, are briefly discussed within the coloring problem approach.}},
author = {{Ponou, Simeon and Doverbratt, Isa and Lidin, Sven and Miller, Gordon J.}},
issn = {{1099-0682}},
keywords = {{Zintl phases; Intermetallic compounds; Germanium; Electronic structure; Coloring problem}},
language = {{eng}},
number = {{1}},
pages = {{169--176}},
publisher = {{John Wiley & Sons Inc.}},
series = {{European Journal of Inorganic Chemistry}},
title = {{Structure and Bonding of an Intergrowth Phase Ca7Ag2+xGe7-x (x approximate to 2/3) Featuring a Zintl-Type Polyanionic Chain}},
url = {{http://dx.doi.org/10.1002/ejic.201501176}},
doi = {{10.1002/ejic.201501176}},
year = {{2016}},
}