Polynitrides

Class of chemical compounds From Wikipedia, the free encyclopedia

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.[1] 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.[2][3]

List

More information Formula, Crystallography ...
Formula Crystallography Properties References
Empirical Structural Notes Crystal Space
group		 Unit cell (Å)
Formula units (Z)[a]
 Volume
(Å3)		 Density
(g·cm−3)
At pressure
(GPa)[b]
Bulk modulus
at zero pressure
(K0) (GPa)
Lowest observed
pressure (GPa)[b]
 Comments
LiN [Li+]2[N2−2] diazenide orthorhombic Immm a=3.1181 b=4.4372 c=10.7912 8 149.30 0 0 black, metallic luster [4]
orthorhombic Cmcm a=3.819 b=6.471 c=3.446 8 85.16 73.6 112(19)[c] 19.0 [5]
LiN2 Li+N−2 N−2 dimers hexagonal P63/mmc a=2.631 c=7.615 2 45.64 21.2 63(4)[c] 4.6 white [5]
LiN5 Li+N−5 pentazolate monoclinic P2 a=3.808 b=3.838 c=2.410

β=99.84°

 1 34.70 73.6 0[d]
73.6 (XRD)		 [5][6]
tr-BeN4 Be2+[poly-N2−4] 1D chains, N4 torsion angle = 17.1° triclinic

(2D layers)

 P1 a=3.275 b=4.212 c=3.704

α=103.43º β=105.61º γ=111.86º

 1 42.4 0 0 [7]
triclinic P1 a=2.4062 b=3.5119 c=3.506

α=104.29° β=111.39° γ=96.71°

 1 26.02 83.5 [7]
m-BeN4 2D infinite sheets of fused N10 rings monoclinic P21/c a=3.283 b=3.2765 c=4.8185

β=99.67°

 2 51.10 96.8 96.8 [7]
Amm2-CN6 2D Amm2 [8]
Amm2-CN10 2D Amm2 [8]
NaN2 Na+N−2 N−2 dimers tetragonal P4/mmm a=3.001 c=4.101 1 36.93 4.0 2.8 black, metallic luster [9]
Na3N8 [Na+]3[N23/4−]4 N20.75- dimers tetragonal I41/amd a=4.9597 c=16.29 4 400.7 27.6 7.7 black, metallic luster [9]
Na2N5 [Na+]2[N2−5] pentazolate-derived dianion monoclinic Pm a=4.781 b=2.5873 c=4.934

β=119.6°

 1 53.1 50.0 18 (Raman)[d] [10][11]
NaN5 Na+N−5 pentazolate orthorhombic Pmn21 a=5.455 b=2.836 c=5.662 2 87.6 52.9 12 (Raman)[d]

25 (XRD)

 [10][11]
NaN7 Na+N−5·N2 pentazolate

nitrogen-inclusion

 monoclinic P21/n a=10.321 b=8.672 c=11.0409

β=91.70°

 16 987.8 52.9 40 [10][11]
α-Mg2N4 [Mg2+]2[a'-N4−4][b'-N4−4] cis-tetranitrogen tetraanion monoclinic P21/n a=7.5182 b=6.5426 c=13.4431

β=130.080°

 2 505.95 0 0 [12]
β-Mg2N4 [Mg2+]2[a-N4−4][b-N4−4] cis-tetranitrogen tetraanion monoclinic P21/n a=7.114 b=5.824 c=8.804

β=104.04°

 2 354.0 58.5 2.3 [12]
MgN4 Mg2+[poly-N2−4] 1D chains, N4 torsion angle = 0°
isoelectronic to polythiazyl
cis-polyacetylene geometry		 orthorhombic Ibam a=3.5860 b=7.526 c=5.1098 1 137.90 58.5 0.9 (Raman)[d]
58.5 (XRD)		 [12][13][7]: Figure S3 
SiN2 Si4+N4−2 pernitride cubic Pa3 a=4.1205 4 69.96 5.327 140 140 [14]
K3N8 [K+]3[N23/4−]4
tetragonal I41/amd a=5.331 c=17.552 4 498.8 27 27 reflective [15]
K2N6 [K+]2[N2−6] planar hexazine dianion hexagonal P6/mmm a=5.281 c=2.661 1 64.27 50
  • 20 (Raman)[d]
  • 21 (XRD)
 reflective [15]
K9N56 [K+]18[N4−6][N−5]14·18N2
orthorhombic Ibam a=5.2380 b=34.560 c=23.205 8 4200.7 61 32 [16]
Sc2N6 triclinic P1 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 [17]
Sc2N8 monoclinic P21/c a=3.3278 b=5.6802 c=7.3964 β=98.905° 2 138.13 4.857 metallic [17]
ScN5 monoclinic P21/m a=3.3225 b=6.440 c=3.7067 β=104.34 2 76.84 4.971 indirect semiconductor [17]
Sc4N3 cubic Fm3m a= 4.2492 4 233.9 6.301 125 [17]
TiN2 Ti4+N4−2 pernitride tetragonal I4/mcm a=4.334 c=5.294 4 99.44 0 385(7)[e] 0 [18][19]
VN2 V4+N4−2 pernitride tetragonal I4/mcm a=4.3015 c=4.9827 4 92.195 5.6883 73.3 347 0 [20][21]
MnN4 chains triclinic P1 a=3.58 b=3.70 c=5.01

α=94.2° β=111.2° γ=71.6°

 58.7 108 GPa [22]
FeN2 orthorhombic Pnnm a=4.431 b=3.722 c=2.421 2 39.93 58.5 [23]
FeN4 Fe2+[poly-N2−4] 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 [23][7]: Figure S3 
CoN2 orthorhombic Pnnm 31 GPa 216 [24]
CoN3 orthorhombic Pnma a=2.555 b=3.463 c=10.655 90-120 GPa [25]
CoN5 monoclinic C2/c a=4.951 b=6.910 c=8.062 β=95.77 90-120 GPa [25]
ZnN4 1D chain orthorhombic Ibam 14-130 GPa [1]
YN6 N189+ rings 100 GPa [26]
Y(N5)3·N2 Y3+[N−5]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 [27]
Y2N11 N-double helix 100 GPa [26]
Y5N14 tetragonal P4/mbm a=8.451 c=4.7316 2 337.93 6.296 50 [28]
Nb2N3 orthorhombic Pnma a=7.897 b=2.857 c=7.660 4 8.755 56 GPa [29]
NbN2 tetragonal I4mm a=2.8365 c=11.444 4 8.723 80 GPa [29]
NbN4 monoclinic P21/n a=4.4827 b=5.4543 c=5.439

β=101.47

 4 7.59 105:100-120 GPa [29]
NbN5 orthorhombic Fdd2 a=11.833 b=13.870 c=3.6001 16 7.323 100-120 GPa [29]
RuN2 Ru4+N4−2 pernitride orthorhombic Pnnm 0 [30]
RhN2 Rh4+N4−2 pernitride orthorhombic Pnnm 235 0 [31]
PdN2 Pd4+N4−2 pernitride Pa3 13 [32]
AgN7 N5 ring + N2 P1 15 GPa 5 black [33]
AgN5 P21/c 15 GPa [33]
AgN4 P1 26.3 GPa 12 [33]
CsN5 Cs+N−5 pentazolate Pbca [34]
CsN5 triclinic P1 [34]
LaN8 N18 rings trigonal R3 [35]
LaN8 N8 cage tetragonal P4/n high energy density [35]
Ce2N6 N4 zigzags C2/m a=5.717 b=4.661 c=6.548

β=93.270

 174.20 ambient [36]
CeN4 chains I41/a a=6.711 c=2.879 0 [37]
CeN6 hexazine R3m a=5.890 c=4.108 [37]
CeN14 sheet hexagonal P6mm a=5.748 c=2.447 [37]
CeN17 sheet hexagonal P6mm a=6.111 c=2.842 [37]
ReN2 [Re5+]2[N4−2][N3−]2 pernitride

nitride

 monoclinic P21/c a=3.625 b=6.407 c=4.948

β=111.48°

 0 330 0 very hard [38]
OsN2 Os4+N4−2 pernitride orthorhombic Pnnm 358 0 [2]
IrN2 Ir4+N4−2 pernitride monoclinic P21/c 428 0 [32][2]
PtN2 Pt4+N4−2 pernitride Pa3 372 0 [39]
PbN2 Pb2+N2−2 diazenide

(provisional, N2x- dimers)

 tetragonal I4/mcm 65[f] 15 [40]
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Notes

  1. [a]
    Based on empirical formula
  2. [b]
    Zero denotes ambient pressure (1 bar = 0.0001 GPa)
  3. [c]
    Extrapolated to zero pressure using the third-order Birch–Murnaghan equation of state
  4. [d]
    Unknown polymorph
  5. [e]
    Modeled using the third-order Birch–Murnaghan equation of state
  6. [f]
    Extrapolated to zero pressure using the second-order Birch–Murnaghan equation of state

References

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