Nitridophosphates MP2 N4 :Eu(2+) (M=Ca, Sr, Ba) and BaSr2 P6 N12 :Eu(2+) have been synthesized at elevated pressures and 1100-1300 °C starting from the corresponding azides and P3 N5 with EuCl2 as dopant. Addition of NH4 Cl as mineralizer allowed for the growth of single crystals. This led to the successful structure elucidation of a highly condensed nitridophosphate from single-crystal X-ray diffraction data (CaP2 N4 :Eu(2+) (P63 , no. 173), a=16.847(2), c=7.8592(16) Å, V=1931.7(6) Å(3) , Z=24, 2033 observed reflections, 176 refined parameters, wR2 =0.096). Upon excitation by UV light, luminescence due to parity-allowed 4f(6) ((7) F)5d(1) →4f(7) ((8) S7/2 ) transition was observed in the orange (CaP2 N4 :Eu(2+) , λmax =575 nm), green (SrP2 N4 :Eu(2+) , λmax =529 nm), and blue regions of the visible spectrum (BaSr2 P6 N12 :Eu(2+) and BaP2 N4 :Eu(2+) , λmax =450 and 460 nm, respectively). Thus, the emission wavelength decreases with increasing ionic radius of the alkaline-earth ions. The corresponding full width at half maximum values (2240-2460 cm(-1) ) are comparable to those of other known Eu(2+) -doped (oxo)nitrides emitting in the same region of the visible spectrum. Following recently described quaternary Ba3 P5 N10 Br:Eu(2+) , this investigation represents the first report on the luminescence of Eu(2+) -doped ternary nitridophosphates. Similarly to nitridosilicates and related oxonitrides, Eu(2+) -doped nitridophosphates may have the potential to be further developed into efficient light-emitting diode phosphors.

BeP(2)N(4) was synthesized in a multi-anvil apparatus starting from Be(3)N(2) and P(3)N(5) at 5 GPa and 1500 degrees C. The compound crystallizes in the phenakite structure type (space group R3, no. 148) with a=1269.45(2) pm, c=834.86(2) pm, V=1165.13(4) x 10(6) pm(3) and Z=18. As isostructural and isovalence-electronic alpha-Si(3)N(4) transforms into beta-Si(3)N(4) at high pressure and temperature, we studied the phase transition of BeP(2)N(4) into the spinel structure type by using density functional theory calculations. The predicted transition pressure of 24 GPa is within the reach of today's state of the art high-pressure experimental setups. Calculations of inverse spinel-type BeP(2)N(4) revealed this polymorph to be always higher in enthalpy than either phenakite-type or spinel-type BeP(2)N(4). The predicted bulk modulus of spinel-type BeP(2)N(4) is in the range of corundum and gamma-Si(3)N(4) and about 40 GPa higher than that of phenakite-type BeP(2)N(4). This finding implies an increase in hardness in analogy to that occurring for the beta- to gamma-Si(3)N(4) transition. In hypothetical spinel-type BeP(2)N(4) the coordination number of phosphorus is increased from 4 to 6. So far only coordination numbers up to 5 have been experimentally realized (gamma-P(3)N(5)), though a sixfold coordination for P has been predicted for hypothetic delta-P(3)N(5). We believe, our findings provide a strong incentive for further high-pressure experiments in the quest for novel hard materials with yet unprecedented structural motives.

Phosphorus nitride imide, PN(NH), is of great scientific importance because it is isosteric with silica (SiO2). Accordingly, a varied structural diversity could be expected. However, only one polymorph of PN(NH) has been reported thus far. Herein, we report on the synthesis and structural investigation of the first high-pressure polymorph of phosphorus nitride imide, β-PN(NH); the compound has been synthesized using the multianvil technique. By adding catalytic amounts of NH4Cl as a mineralizer, it became possible to grow single crystals of β-PN(NH), which allowed the first complete structural elucidation of a highly condensed phosphorus nitride from single-crystal X-ray diffraction data. The structure was confirmed by FTIR and (31)P and (1)H solid-state NMR spectroscopy. We are confident that high-pressure/high-temperature reactions could lead to new polymorphs of PN(NH) containing five-fold- or even six-fold-coordinated phosphorus atoms and thus rivalling or even surpassing the structural variety of SiO2.

The ternary transition-metal nitridophosphates CdP 2 N 4 and MnP 2 N 4 have been synthesized under high-pressure high-temperature conditions (5-8 GPa, 1000-1300°C) by using the multianvil technique. Cd and Mn azides can be used as the starting materials, however, with respect to safety considerations, it is much more advantageous to start from metal powders and phosphorus nitride imide, HPN 2 . Both nitridophosphates crystallize in a structure closely related to the mega calsilite structure type. As a result of the known issues concerning superstructures with this type of structure, TEM investigations were performed on CdP 2 N 4 , which revealed that the megacalsilite superstructure is not equally pronounced in all [a]

Phosphorus nitride imide, PN(NH), is of great scientific importance because it is isosteric with silica (SiO 2 ). Accordingly, a varied structural diversity could be expected. However, only one polymorph of PN(NH) has been reported thus far. Herein, we report on the synthesis and structural investigation of the first high-pressure polymorph of phosphorus nitride imide, b-PN(NH); the compound has been synthesized using the multianvil technique. By adding catalytic amounts of NH 4 Cl as a mineralizer, it became possible to grow single crystals of b-PN(NH), which allowed the first complete structural elucidation of a highly condensed phosphorus nitride from single-crystal X-ray diffraction data. The structure was confirmed by FTIR and 31 P and 1 H solid-state NMR spectroscopy. We are confident that high-pressure/high-temperature reactions could lead to new polymorphs of PN(NH) containing five-fold-or even six-fold-coordinated phosphorus atoms and thus rivalling or even surpassing the structural variety of SiO 2 .