Li₄Ca₃Si₂N₆ and Li₄Sr₃Si₂N₆ – Quaternary Lithium Nitridosilicates with Isolated [Si₂N₆]^10– Ions

Abstract

The isotypic nitridosilicates Li 4 Ca 3 Si 2 N 6 and Li 4 Sr 3 Si 2 N 6 were synthesized by reaction of Sr

Structural Relationship between the Mg‐Containing Nitridosilicates Ca2Mg[Li4Si2N6] and Li2Ca2[Mg2Si2N6]

“…The crystal structure of Ca 2 Mg[Li 4 Si 2 N 6 ] (see Figure 1) consists of [Si 2 N 6 ] 10– bow‐tie units. This structural motif was first described by DiSalvo et al in Ba 5 Si 2 N 6 12,15–17. Caused by edge sharing of the SiN 4 tetrahedra in Ca 2 Mg[Li 4 Si 2 N 6 ] the corresponding angle N2–Si–N2 is reduced to a value of 93.81(8)° and the involved Si–N2 distances are elongated and range from 1.80–1.83 Å.…”

“…This results in a rather short Si–Si distance of 2.4772(12) Å. All of these features can be observed for other bow‐tie type nitridosilicates as well 12,15–17. Especially the structurally related Ca 3 [Li 4 Si 2 N 6 ] shows good accordance with a reduced angle N–Si–N of 95.9°, a Si–N bond length of 1.83 Å, and a Si–Si distance of 2.45 Å 12.…”

“…Ca 2 Mg[Li 4 Si 2 N 6 ] and Li 2 Ca 2 [Mg 2 Si 2 N 6 ] have homeotypic crystal structures and exhibit structural features of the nitridolithosilicate Ca 3 [Li 4 Si 2 N 6 ];12 a detailed comparison will be given later. Ca 2 Mg[Li 4 Si 2 N 6 ] is isomorphic to Ca 3 [Li 4 Si 2 N 6 ] with one Ca 2+ being formally replaced by Mg 2+ .…”

“…The nitridolithosilicate Ca 2 Mg[Li 4 Si 2 N 6 ] is only the second example with Mg 2+ acting as a counterion for the anionic nitridosilicate substructure. Furthermore, it is shown how both crystal structures can be derived from the aristotype Ca 3 [Li 4 Si 2 N 6 ] 12…”

Structural, elastic, electronic and optical properties of the quaternary nitridogallate LiCaGaN2: First-principles study

“…Four strain patterns -one with nonzero 11 ε and 12 ε components, the second with nonzero 33 ε and 12 ε , the third with nonzero 22 ε and the fourth with nonzero 31 ε -are sufficient to cause stresses related to all 13 independent elastic constants for a monoclinic structure, namely C 11 , C 22 , C 33 , C 44 , C 55 , C 66 , C 12 , C 13 , C 15 , C 23 , C 25 , C 11 and C 35 . Three positive and three negative amplitudes are used for each strain component with a maximum strain value of 0.5% and the elastic constants are determined from a linear fit of the calculated stress as a function of strain.…”