Structure and Chemical Bonding of Alkaline-Earth Digallides

2008 ◽  
Vol 634 (11) ◽  
pp. 2022-2022
Author(s):  
Frank Haarmann ◽  
Katrin Koch ◽  
Daniel Grüner ◽  
Walter Schnelle ◽  
Oliver Pecher ◽  
...  
Keyword(s):  
Chemical Bonding ◽  
Alkaline Earth

scholarly journals Electric dipole moments and chemical bonding of diatomic alkali–alkaline earth molecules

2016 ◽  
Vol 18 (8) ◽  
pp. 5964-5973 ◽  
Author(s):  
Johann V. Pototschnig ◽  
Andreas W. Hauser ◽  
Wolfgang E. Ernst
Keyword(s):  
Dipole Moment ◽  
Electric Dipole Moment ◽  
Electric Dipole ◽  
Chemical Bonding ◽  
Alkaline Earth ◽  
Dipole Moments ◽  
Electric Dipole Moments ◽  
Permanent Electric Dipole Moment

In the present study we investigated the permanent electric dipole moment and other properties of several alkali–alkaline earth molecules in the lowest Σ+ state of the doublet and quartet multiplicity.

Trigermanides AEGe3 (AE = Ca, Sr, Ba): chemical bonding and superconductivity

2016 ◽  
Vol 71 (5) ◽  
pp. 585-592 ◽  
Author(s):  
Rodrigo Castillo ◽  
Walter Schnelle ◽  
Alexey I. Baranov ◽  
Ulrich Burkhardt ◽  
Matej Bobnar ◽  
...  
Keyword(s):  
Chemical Bonding ◽  
Alkaline Earth ◽  
Lone Pair ◽  
Earth Metal ◽  
Alkaline Earth Metal ◽  
Superconducting Transition ◽  
Metal Atoms ◽  
Atomic Interactions ◽  
Electron Compounds ◽  
Alkaline Earth Cations

AbstractThe crystal structures of the trigermanides AEGe3(tI32) (AE = Ca, Sr, Ba; space group I4/mmm, for SrGe3: a = 7.7873(1), c = 12.0622(3) Å) comprise Ge2 dumbbells forming layered Ge substructures which enclose embedded AE atoms. The chemical bonding analysis by application of the electron localizability approach reveals a substantial charge transfer from the AE atoms to the germanium substructure. The bonding within the dumbbells is of the covalent two-center type. A detailed analysis of SrGe3 reveals that the interaction on the bond-opposite side of the Ge2 groups is not lone pair-like – as it would be expected from the Zintl-like interpretation of the crystal structure with anionic Ge layers separated by alkaline-earth cations – but multi-center strongly polar between the Ge2 dumbbells and the adjacent metal atoms. Similar atomic interactions are present in CaGe3 and BaGe3. The variation of the alkaline-earth metal has a merely insignificant influence on the superconducting transition temperatures in the s,p-electron compounds AEGe3.

scholarly journals Mixed Alkaline Earth Germanides A2MGe2(A= Ca/Sr; M= Sn,Pb)

2014 ◽  
Vol 70 (a1) ◽  
pp. C1701-C1701
Author(s):  
Michael Jehle ◽  
Michael Langenmaier ◽  
Julia Steckhan ◽  
Caroline Röhr
Keyword(s):  
Band Structure ◽  
Chemical Bonding ◽  
Alkaline Earth ◽  
Radius Ratio ◽  
Zigzag Chain ◽  
Band Structure Calculations ◽  
Square Planar ◽  
New Type ◽  
Bottom Left ◽  
Structure Calculations

The crystal structures of the mixed alkaline earth tetrelides with the composition (CaxSr1-x)2MGe2 (M= Sn,Pb) exhibit identically stacked planes consisting of square planar coordinated M atoms (light gray) and [Ge]m zigzag chain pieces of varying lengths m. Each Ge atom is thereby coordinated by A atoms forming trigonal prisms (dark gray). The chain length m depends on the radius ratio rM4-/rA2+ (rr), whereat the M4- radius was estimated from the average Ca-M distances in the structures of Ca2M, which exhibit isolated tetrel anions. Depending on this radius ratio the structures of the title compounds feature [Ge]m chains of lengths m of 2, 4, 6 and infinite. Starting with Ge-Ge dumbbells in Ca2SnGe2 (rr= 1.57, space group P4/mbm, a= 748.58(13), c= 445.59)(8) pm, R1= 0.060, Mo2FeB2 type; cf. also Yb2SnGe2 [1], fig. top left), (Ca0.58Sr0.42)2SnGe2 shows Ge4 zigzag chain pieces (rr= 1.50, Pbam, a= 781.01(2), b= 1477.95(3), c= 457.00(1) pm, R1= 0.018, La2NiIn2 type; cf. also (Ca0.34Eu0.66)2PbGe2 [2], fig. bottom left). Ge6 pieces are present in (Ca0.23Sr0.77)2PbGe2 (rr= 1.48, Pbam, a= 2311.20(15), b= 791.64(5), c= 458.53(3) pm, R1= 0.073, new type, fig. top right) and infinit Ge chains in (CaxSr1-x)2PbGe2 (rr= 1.44-1.46, x= 0 to 0.22, Cmmm; for x= 0: a= 402.36(11), b= 1542.29(42), c= 463.27(10) pm, R1= 0.064, Mn2AlB2 type; cf. also (Sr0.21Eu0.79)2PbGe2 [2], fig. bottom right). In this series, i.e. with increasing m, the connectivity of M changes from a square planar coordination by four Ge in Ca2SnGe2 ([MGe4]) via [MGe3M] in (Ca0.58Sr0.42)2SnGe2 and [MGe3M]2[MGe2M2] in (Ca0.23Sr0.77)2PbGe2 up to [MGe2M2] in Sr2PbGe2, finally. The details of chemical bonding are discussed on the basis of band structure calculations.

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