Polynitrides

Polynitrides are solid chemical compounds with a large amount of nitrogen, beyond what would be expected from valencies. Some with N2 ions are termed pernitrides. Azides are not considered polynitrides, although pentazolates are.

They are formed at high pressures and mostly at high temperature. Many are stable under high pressure, but some are metastable when decompressed to standard conditions. They are high energy density materials, capable of exploding with high power. Some are very hard, almost as strong as diamond.

Nitrogen anions can take the form of diazenide , pentazolate , 1-dimensional chains , hexazine dianion , pernitride and even include dinitrogen molecules.

List

FormulaCrystallographyPropertiesReferencesEmpiricalStructuralNotesCrystalSpacegroupUnit cell (Å)Volume(Å3)Density(g·cm−3)class="unsortable"!CommentsLiNdiazenideorthorhombicImmma=3.1181 b=4.4372 c=10.79128149.3000black, metallic lusterorthorhombicCmcma=3.819 b=6.471 c=3.446885.1673.6112(19)19.0LiN2 dimershexagonalP63/mmca=2.631 c=7.615245.6421.263(4)4.6whiteLiN5pentazolatemonoclinicP2a=3.808 b=3.838 c=2.410 β=99.84°134.7073.6073.6 (XRD)tr-BeN41D chains, N4 torsion angle = 17.1°triclinic (2D layers)Pa=3.275 b=4.212 c=3.704 α=103.43º β=105.61º γ=111.86º142.400triclinicPa=2.4062 b=3.5119 c=3.506 α=104.29° β=111.39° γ=96.71°126.0283.5m-BeN42D infinite sheets of fused N10 ringsmonoclinicP21/ca=3.283 b=3.2765 c=4.8185 β=99.67°251.1096.896.8Amm2-CN62DAmm2Amm2-CN102DAmm2NaN2 dimerstetragonalP4/mmma=3.001 c=4.101136.934.02.8black, metallic lusterNa3N8N20.75- dimerstetragonalI41/amda=4.9597 c=16.294400.727.67.7black, metallic lusterNa2N5pentazolate-derived dianionmonoclinicPma=4.781 b=2.5873 c=4.934 β=119.6°153.150.018 (Raman)NaN5pentazolateorthorhombicPmn21a=5.455 b=2.836 c=5.662287.652.912 (Raman) 25 (XRD)NaN7pentazolate nitrogen-inclusionmonoclinicP21/na=10.321 b=8.672 c=11.0409 β=91.70°16987.852.940α-Mg2N4[Mg(2+)]2[a\'''\-N4(4-)][b\'\-N4(4-)]}} |cis-tetranitrogen tetraanion |monoclinic |P21/n|a=7.5182 b=6.5426 c=13.4431β=130.080° |2 |505.95 | |0 | |0

|β-Mg2N4 | |cis-tetranitrogen tetraanion |monoclinic |P21/n|a=7.114 b=5.824 c=8.804β=104.04° |2 |354.0 | |58.5 | |2.3

|MgN4 | |1D chains, N4 torsion angle = 0°isoelectronic to polythiazylcis-polyacetylene geometry |orthorhombic |Ibam|a=3.5860 b=7.526 c=5.1098 |1 |137.90 | |58.5 | |0.9 (Raman)58.5 (XRD)

|SiN2 | |pernitride |cubic |Pa|a=4.1205 |4 |69.96 |5.327 |140 | |140

|K3N8

|tetragonal |I41/amd|a=5.331 c=17.552 |4 |498.8 | |27 | |27 |reflective

|K2N6 | |planar hexazine dianion |hexagonal |P6/mmm|a=5.281 c=2.661 |1 |64.27 | |50

|reflective

|K9N56

|orthorhombic |Ibam|a=5.2380 b=34.560 c=23.205 |8 |4200.7 | |61 | |32

|Sc2N6

|triclinic |P|a=2.9170 b=4.328 c=4.812 α=99.36 β=104.29 γ=99.52 |1 |56.73 |5.093 |78

|metallic

|Sc2N8

|monoclinic |P21/c|a=3.3278 b=5.6802 c=7.3964 β=98.905° |2 |138.13 |4.857

|metallic

|ScN5

|monoclinic |P21/m|a=3.3225 b=6.440 c=3.7067 β=104.34 |2 |76.84 |4.971

|indirect semiconductor

|Sc4N3

|cubic |Fmm|a= 4.2492 |4 |233.9 |6.301 |125

|TiN2 | |pernitride |tetragonal |I4/mcm|a=4.334 c=5.294 |4 |99.44 | |0 |385(7) |0

|VN2 | |pernitride |tetragonal |I4/mcm|a=4.3015 c=4.9827 |4 |92.195 |5.6883 |73.3 |347 |0

|MnN4 | |chains |triclinic |P|a=3.58 b=3.70 c=5.01 α=94.2° β=111.2° γ=71.6° | |58.7 | |108 GPa

|FeN2

|orthorhombic |Pnnm|a=4.431 b=3.722 c=2.421 |2 |39.93 | |58.5

|FeN4 | |1D chains, N4 torsion angle = 36°polytetrazene geometry |triclinic | |a=2.5089 b=3.524 c=3.5409 105.08 110.26 92.03 |1 |28.09 | |106

|CoN2

|orthorhombic |Pnnm|

|31 GPa |216

|CoN3

|orthorhombic |Pnma|a=2.555 b=3.463 c=10.655

|90-120 GPa

|CoN5

|monoclinic |C2/c|a=4.951 b=6.910 c=8.062 β=95.77

|90-120 GPa

|36 GPa

|14-130 GPa

|YN6 | |N189+ rings

|100 GPa

|Y(N5)3·N2 | |pentazolate nitrogen-inclusion |monoclinic |P21/c|a=9.617 b=6.932 c=6.609 β=95.13° |4 |438.8 |5.092 |125 GPa

|Y2N11 | |N-double helix

|100 GPa

|Y5N14

|tetragonal |P4/mbm|a=8.451 c=4.7316 |2 |337.93 |6.296 |50

|Nb2N3

|orthorhombic |Pnma|a=7.897 b=2.857 c=7.660 |4 | |8.755 |56 GPa

|NbN2

|tetragonal |I4mm|a=2.8365 c=11.444 |4 | |8.723 |80 GPa

|NbN4

|monoclinic |P21/n|a=4.4827 b=5.4543 c=5.439β=101.47 |4 | |7.59 |105:100-120 GPa

|NbN5

|orthorhombic |Fdd2 |a=11.833 b=13.870 c=3.6001 |16 | |7.323 |100-120 GPa

|235 |0

|RhN2 | |pernitride |monoclinic |P21/c|

|PdN2 | |pernitride | |Pa|

|13

|AgN7 |N5 ring + N2

|P1

|15 GPa | |5 |black

|AgN5

|P21/c|

|15 GPa

|AgN4

|P|

|26.3 GPa | |12

|SbN4 |Sb25+N810- |N8 chains |monoclinic |P21/n|

|100-120 GPa

|CsN5

|triclinic |P|

|LaN8 | |N18 rings |trigonal |R|

|LaN8 | |N8 cage |tetragonal |P4/n|

|high energy density

|Ce2N6 | |N4 zigzags | |C2/m|a=5.717 b=4.661 c=6.548β=93.270 | |174.20 | |ambient

|CeN4 | |chains | |I41/a|a=6.711 c=2.879

|CeN6 | |hexazine | |Rm|a=5.890 c=4.108

|CeN14 | |sheet |hexagonal |P6mm|a=5.748 c=2.447

|CeN17 | |sheet |hexagonal |P6mm|a=6.111 c=2.842

|Hf2N11 | |N double helix |hexagonal |P6422

|TaN4 | |N4 chains |monoclinic |P21/n|

|100

|TaN5 | |branched infinite chains |orthorhombic |Fdd2

|100

|WN6 | |N66- hexaazacyclohexane derivative |rhombohedral |Rm|

|0 |330 |0 |very hard

|175

|105-130 GPa

|358 |0

|IrN2 | |pernitride |monoclinic |P21/c|

|428 |0

|PtN2 | |pernitride | |Pa|

|372 |0

Notes

References

Polynitrides

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