Local order in Sr<sub>1−x</sub>Ga<sub>2+3x</sub>

Haarmann, Frank; Prots, Yurii

doi:10.1002/zaac.200670118

Cited by 13 publications

(13 citation statements)

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“…The Sr compound differs by possessing a homogeneity range Sr 1Àx Ga 2 + 3x with 0 x 0.076 at 950 8C. [6] Metallographic observations agree well with these results. For the remaining part of the manuscript we will focus on the compounds with stoichiometric composition 1:2 and denote the sample Sr 1Àx Ga 2 + 3x with x = 0 as SrGa 2 .…”

Section: Resultssupporting

confidence: 85%

“…[5] The transition from 3D frameworks to planar 2D nets of Ga atoms is realized in the homogeneity range of Sr 1Àx Ga 2 + 3x . [6] Triangular Ga 3 units substitute the cations and connect the Abstract: Combined application of 69,71 Ga NMR spectroscopy and quantum mechanical calculations reveals the chemical bonding in the digallides of Ca, Sr, and Ba. An analysis of the electron localization function (ELF) shows honeycomb-like 6 3 nets of the Ga atoms as the most prominent structural features in SrGa 2 and BaGa 2 .…”

Section: Introductionmentioning

confidence: 99%

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Electronic Structure, Chemical Bonding, and Solid‐State NMR Spectroscopy of the Digallides of Ca, Sr, and Ba

Haarmann

Koch

Grüner

et al. 2009

Chemistry A European J

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Combined application of (69,71)Ga NMR spectroscopy and quantum mechanical calculations reveals the chemical bonding in the digallides of Ca, Sr, and Ba. An analysis of the electron localization function (ELF) shows honeycomb-like 6(3) nets of the Ga atoms as the most prominent structural features in SrGa(2) and BaGa(2). For CaGa(2) a description of a 3+1-coordinated Ga atom is revealed by the ELF and by an analysis of interatomic distances. The NMR spectroscopic signal shift is mainly due to the Knight shift and is almost equal for the investigated digallides, whereas the anisotropy of the signal shift decreases with the radius of the alkaline-earth metals. Calculated and observed values of the electric field gradient (EFG) are in good agreement for CaGa(2) and BaGa(2) but differ by about 21 % for SrGa(2) indicating structural instability. Better agreement is achieved by considering a puckering of the Ga layers. For BaGa(2) an instability of the structure is indicated by a peak in the density of states at the Fermi level, which is shifted to lower energies when taking puckering of the Ga layers into account. Both structural modifications are confirmed by crystallographic information. The Fermi velocity of the electrons is strongly anisotropic and is largest in the (001) plane of the crystal structure. This results in an alignment of the crystallites with the [001] axis perpendicular to the magnetic field as observed in (69,71)Ga NMR spectroscopy and magnetic susceptibility experiments. The electron transport is predominantly mediated by the Ga-Ga p(x)- and p(y)-like electrons in the (001) plane. The specific heat capacity of BaGa(2) was determined and indicated the absence of phase transitions between 1.8 and 320 K.

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Section: Resultssupporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Electronic Structure, Chemical Bonding, and Solid‐State NMR Spectroscopy of the Digallides of Ca, Sr, and Ba

Haarmann

Koch

Grüner

et al. 2009

Chemistry A European J

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“…The composition of the compound, the fractional occupation of the Sr1, Ga5 and Ga6 sites and the interatomic distances indicate a substitution of one Sr1 atom by three Ga atoms. This type of substitution of the cations by Ga3 triangular units was also recently found in Eu 1x Ga 2+3x with x = 0.08 [8], in Eu 3x Ga 8+3x with x = 0.12 [9] and in Sr1xGa2+3x with x up to 0.056 [10]. …”

Section: Discussionsupporting

confidence: 79%

Crystal structure of tristrontium octagallide, Sr3-xGa8+3x (x = 0.15)

Haarmann

Prots

Göbel

et al. 2006

Zeitschrift Für Kristallographie - New Crystal Structures

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Ga8.45Sr2.85, orthorhombic, Immm (no. 71), a = 4.3958(9) Å, b = 4.5298(6) Å, c = 26.002(4) Å, V = 517.8 Å 3 , Z = 2, Rgt(F) = 0.038, wRref(F 2 ) = 0.091, T = 293 K. Source of materialThree samples of Sr3xGa8+3x with x = 0.07, 0.15 and 0.20 labeled as I, II and III, respectively, were prepared by melting of appropriate mixtures of the elements in welded Ta container in a high frequency furnace. After one week of thermal annealing at 800°C they were quenched in ice water. According to the results of X-ray powder diffraction (Huber Guinier G670, CuK a1 radiation, l = 1.540598 Å) and metallographic investigations sample II was single phase containing the title compound while samples I and III included admixtures of Sr 1x Ga 2+3x and SrGa 4 , respectively. Single crystals for X-ray diffraction were isolated from sample II. The material is gray with metallic luster. Due to the sensitivity regarding oxidation the samples were handled under inert conditions. Experimental detailsAs starting values for structure refinement we used the atomic positions observed in Eu 3 Ga 8 [1,2] which realizes a binary variant of the U3Ni4Si4 type [3]. In the advanced steps of the refinement some additional peaks in hexagon-like arrangement were observed on the difference Fourier maps in the vicinity of Sr1 atoms (figure, top left). These correspond to two crystallographically independent Ga positions with partial occupation. This structural feature is accompanied by a reduced occupation of the Sr1 site. The lattice parameter of the compounds were determined with LaB6 as internal standard (a = 4.15692 Å). They agree well for the different samples indicating the absence of a significant homogeneity range (sample I: a = 4.3983 (7)

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“…The composition of the compound, the fractional occupation of the Sri, Ga5 and Ga6 sites and the interatomic distances indicate a substitution of one Sri atom by three Ga atoms. This type of substitution of the cations by Ga3 triangular units was also recently found in Eui-*Ga2+3* with χ = 0.08 [8], in Eu3-*Ga8+3i with χ = 0.12 [9] and in Sri-xGa 2+ 3x with χ up to 0.056 [10]. …”

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confidence: 81%

Crystal structure of tristrontium octagallide, Sr3-x+Ga8+3x(x = 0.15)

Haarmann¹,

Prots²,

Göbel³

et al. 2006

Zeitschrift Für Kristallographie - New Crystal Structures

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Ga8.45Sr2.85, orthorhombic, Immm (no. 71), a = 4.3958(9) A, b = 4.5298(6)A, c = 26.002(4)Ä, V= 517.8 Ä 3 ,Ζ = 2, Rgt(F) = 0.038, wR^F 2 ) = 0.091, 7" =293 Κ. Source of materialThree samples of Sr3_,Ga8+3 X with χ = 0.07,0.15 and 0.20 labeled as I, II and III, respectively, were prepared by melting of appropriate mixtures of the elements in welded Ta container in a high frequency furnace. After one week of thermal annealing at 800 °C they were quenched in ice water. According to the results of X-ray powder diffraction (Huber Guinier G670, CuKai radiation, λ = 1.540598 Λ) and metallographic investigations sample II was single phase containing the title compound while samples I and III included admixtures of Sri_xGa2+3x and SrGa4, respectively. Single crystals for X-ray diffraction were isolated from sample II. The material is gray with metallic luster. Due to the sensitivity regarding oxidation the samples were handled under inert conditions. Experimental detailsAs starting values for structure refinement we used the atomic positions observed in EuaGae [1,2] which realizes a binary variant of the LbNUSLt type [3]. In the advanced steps of the refinement some additional peaks in hexagon-like arrangement were observed on the difference Fourier maps in the vicinity of Sri atoms (figure, top left). These correspond to two crystallographically independent Ga positions with partial occupation. This structural feature is accompanied by a reduced occupation of the Sri site. The lattice parameter of the compounds were determined with LaBe as internal standard (a = 4.15692 Ä). They agree well for the different samples indicating the absence of a significant homogeneity range (sample I: a = 4.3983 (7) DiscussionThe main motif of Sr3-*Ga8+3* reproduces those of the l^NUSu structure type [3]. It can be described as an intergrowth of AIB2[4] and BaAL» [5] type fragments being realized by the so far known neighboring phases SrGa2 and SrGa4 [6]. The Ga atoms form a regular 3D framework by four-and six-membered rings based on three-(Gal and Ga2) four-(Ga2) and five-fold (Ga4) coordinated Ga atoms. The Ga-Ga contacts within the framework are in the range of 2.5162(8) A -2.6902(8) A being smaller than the average distances

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Local order in Sr_1−xGa_2+3x

Cited by 13 publications

References 2 publications

Electronic Structure, Chemical Bonding, and Solid‐State NMR Spectroscopy of the Digallides of Ca, Sr, and Ba

Electronic Structure, Chemical Bonding, and Solid‐State NMR Spectroscopy of the Digallides of Ca, Sr, and Ba

Crystal structure of tristrontium octagallide, Sr3-xGa8+3x (x = 0.15)

Crystal structure of tristrontium octagallide, Sr3-x+Ga8+3x(x = 0.15)

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Local order in Sr1−xGa2+3x

Cited by 13 publications

References 2 publications

Electronic Structure, Chemical Bonding, and Solid‐State NMR Spectroscopy of the Digallides of Ca, Sr, and Ba

Electronic Structure, Chemical Bonding, and Solid‐State NMR Spectroscopy of the Digallides of Ca, Sr, and Ba

Crystal structure of tristrontium octagallide, Sr3-xGa8+3x (x = 0.15)

Crystal structure of tristrontium octagallide, Sr3-x+Ga8+3x(x = 0.15)

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Local order in Sr_1−xGa_2+3x