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Within the framework of density functional theory, electronic structure of beryllium nitride in β phase (β-Be3N2) is determined, and on the base of the electric structures, a number of key optical properties of β-Be3N2 are calculated, with the method of full-potential linearized augmented plane wave under the random phase approximation for the boundaries and the generalized gradient approximation for the exchange-correlation potentials. The calculated optical properties as a function of frequency include the real and imaginary parts of the dielectric function e(ω), the refraction index n(ω), the extinction coefficient κ(ω), the reflectivity R(ω), the energy loss function L(ω), and the absorption coefficient I(ω) along the a and c directions of the primitive cell presenting the β-Be3N2 crystals. It is demonstrated that the optical properties of β-Be3N2 appear anisotropic for energies

Polynitrogens are the ideal rocket fuels or propellants. Due to strong triple N≡N bond in N 2 , the direct polymerization of nitrogen is rather difficult (i.e. extreme high temperature and high pressure). However, the use of nitrides as precursors or the reaction of N 2 with other elements has been proved to be an effective way to obtain polynitrogens. Here, with assistance of the advanced first-principles swarm-intelligence structure searches, we found that P 1 ¯ -BeN 4 , containing infinite zigzag-like polymeric nitrogen chains, can be synthesized by compressing the mixture of Be 3 N 2 and N 2 at 25.4 GPa, which is greatly lower than 110 GPa for synthesizing cubic gauche nitrogen and other polynitrogen compounds (e.g. bulk CNO at 52 GPa and SN 4 at 49 GPa). Its structural stability can be attributed to the coexistence of ionic Be-N and covalent N-N bonds. Intriguingly, this phase has high kinetic stability and remains metastable at ambient pressure. The exceptional properties, including high energy density (3.60 kJ g −1 ), high nitrogen content (86.1%), high dynamical stability, and low polymerization pressure, make P 1 ¯ -structured BeN 4 a promising high energy material. Infinite nitrogen chains in P 1 ¯ -BeN 4 transform to N 10 rings network in P 2 1 / c phase at 115.1 GPa. P 1 ¯ -BeN 4 is metallic, while P 2 1 / c -BeN 4 is an insulator.

Secondary phase particles of beryllium nitride and beryllium carbide in beryllium were analyzed by Auger Electron Spectroscopy. Survey spectra as well as high resolution Be KLL, N KLL and C KLL transitions were collected and are presented. The primary beryllium KLL Auger transitions for the nitride and carbide were recorded at 96.7 and 100.4 eV respectively. The homogeneity and composition of the secondary phase particles was confirmed by energy dispersive x-ray spectroscopy.

Beryllium-nitride (Be 3 N 2 ) thin films were grown on silicon Si(1 1 1) substrates by pulsed laser deposition in a RIBER LDM-32 system, and characterized with in/ex situ XPS and SIMS. The structure of the films was analyzed with XRD. The films were further analyzed for surface topographic information with SEM and profilometry, and for optical properties with optical spectroscopy. It was observed that the material, prepared at room temperature and annealed at 700 °C for 2 h, had undergone a partial phase transition to a mixture of amorphous and crystalline phases, and the thin films showed a large anti-reflection window in the visible. Therefore, the annealed Be 3 N 2 thin films would be potentially useful for stable electronic packaging with desired photonic features.

Highly luminescent beryllium nitride powder (Be 3 N 2 ) has been synthesized by direct nitridation of metallic beryllium with ultra-high purity ammonia (NH 3 ) in a horizontal quartz tube reactor at 1100 °C. The calculated Gibbs free energy for this reaction at 1100 °C is −602.20 kJ/mol and the equilibrium constant is 2.7×10 22 , this make workable the process at the conditions chosen for this synthesis. The Be 3 N 2 produced by this method is a light-gray powder which showed the typical high hardness of this material. The Be 3 N 2 powders synthesized in this research consist mostly of agglomerates formed of regular cubic polyhedrons between one and two microns long each as shown by electron microscopy. These crystallites have a cubic structure as shown by X-ray diffraction and exhibit high intensity room temperature cathodoluminescence with a peak around 356 nm (3.48 eV), which is related to their near-band-edge emission. These properties make this material a strong candidate for wide-band optoelectronic applications such as ultraviolet-lasers, sensors and light-emitting diodes.

Be3N2 thin films have been grown on Si(1 1 1) substrates using the pulsed laser deposition method at different substrate temperatures: room temperature (RT), 200 ◦ C, 400 ◦ C, 600 ◦ C and 700 ◦

We have performed extensively crystal structure prediction on Be 3 N 2 to uncover two novel superhard polymorphs with rhombohedral ( R 3 m ) and hexagonal ( P- 3 m 1) symmetries, which are energetically much superior to previously proposed γ-Be 3 N 2 and stable against decomposition into a mixture of 3Be + N 2 . The calculated Vickers hardness for the two predicted phases is beyond 50 GPa, exceeding that of well-known superhard materials B 6 O. Thermodynamic study suggests that the P -3 m 1 phase becomes most stable above 118 GPa.

Extreme ultraviolet and soft X-ray optical systems require low absorbing materials for many technological applications. In this paper, the optical properties of beryllium nitride (Be3N2) are studied and compared with those of beryllium (Be), a widely used material in this context. Thus, the dielectric function of Be and Be3N2 are determined in the 4–100 eV energy interval by means of reflection electron energy loss spectroscopy. It is found that the absorption coefficient of Be and Be3N2 are similar in the 40–100 eV energies range. Thereafter, the superior chemical stability and mechanical properties of Be3N2 makes it a promising Be substitute as optical material in severe environments.

In situ Auger electron, x-ray photoelectron, and electron energy loss spectroscopic data were obtained on epitaxial α-Be3N2 layers grown on (111) and (100) silicon substrates. Films were grown by laser ablating a beryllium foil in molecular nitrogen ambient at 750 °C. The ultrahigh vacuum laser ablation growth system is attached to an analysis chamber equipped with an e-gun, an x-ray source (dual anode Mn/Al), and an electron analyzer MAC-3, all from CAMECA. The spectra show that the film surface is free of impurities, except for traces, of oxygen. Quantitative XPS analysis for the film yields 61, 35, and 4 at % for beryllium, nitrogen, and oxygen concentrations, respectively.

The electronic and structural properties of beryllium nitride (alpha and beta), magnesium- and calcium-nitrides were investigated using first principle full potential-linearized augmented plane wave method within density functional theory. We used Perdew and Wang-generalized gradient approximation, which is based on exchange correlation energy optimization, to calculate the total energy and the Engel–Vosko's GGA formalism, which optimize the corresponding potential, for band structure calculations. We also optimized internal parameters by relaxing the atomic positions in the force directions. Our results including lattice parameter, bulk modulus and it's pressure derivative, cohesive energy, band structure and density of states are compared with the experimental and other theoretical (Hartree–Fock approximation with a posteriori density functional correction) data.

Beryllium nitride thin films, which are candidates for optoelectronic applications, have been grown by pulsed laser deposition on silicon substrates. The films were prepared by ablating a beryllium foil in N environment at several pressures and substrate 2 temperatures. Real-time ellipsometric monitoring for the period of deposition were carried out by a multiwavelength ellipsometer in the 1.625(hn(4.405 eV photon-energy range. After its completion, the films were characterized in situ by electron spectroscopies and ex situ by atomic force and scanning electron microcopies. A model for the growth of beryllium nitride was applied to reproduce the optical measurement and concurrently, the refractive index from the visible to the near ultraviolet spectral region was calculated. The estimated optical bandgap correlates closely with previously published theoretical results. 2003 Elsevier Science B.V. All rights reserved.

The ground state electronic structure of the beryllium nitride alpha phase has been investigated using the all-electron ab initio periodic Hartree–Fock (HF) approach, with a posteriori density-functional (DFT) correlation corrections. The computed HF lattice constant (8.144 A) agrees with experiment (8.145 A) and the calculations predict a bulk modulus of 2.52 Mbar and cohesive energy of 1.24 a.u./formula unit. The band gap is found to be direct of 4.43 eV at the Γ point, including corrections with DFT. This material might have application in the area of optoelectronics.

We have investigated the electronic properties, in different crystal phases of the ${\mathrm{Be}}_{3}{\mathrm{N}}_{2}$ (alpha and beta), AlN (wurtzite and zinc blende) and ${\mathrm{Mg}}_{3}{\mathrm{N}}_{2},$ compounds within an all-electron ab initio linear combination of atomic orbitals self-consistent-field-Hartree-Fock approximation with a posteriori density-functional correction. Results include lattice parameters, bulk moduli and its derivative, band structure, density-of-states, charge density, and Mulliken population analysis. We also presented aluminum nitride band calculations obtained by various methods, showing that our results lie within previously calculated values and in good agreement with experimental data. Addionally the alpha phase of beryllium nitride, presents a direct band gap of 4.47 eV and might have application in blue/UV light-emitting diodes and lasers.

Herein we report the construction of a Wagner chemical state plot for beryllium containing the: metallic, oxide, nitride and carbide forms of beryllium by combining electron beam induced AES and XPS data. AES and XPS values were collected from metallic beryllium mechanically abraded in vacuum, bulk and native beryllium oxide and homogeneous secondary-phase beryllium nitride and beryllium carbide inclusions. XPS data for beryllium nitride and carbide were obtained from the literature.

Recent successful experiments with nitrogen as a seeding gas in fusion plasma devices, together with the decision to use beryllium as an armor material in the international fusion experiment ITER, have triggered interest in interactions of energetic N ions with Be and the influence of possible compound formation on parameters relevant to reactor operation and safety. Laboratory experiments are performed to investigate the properties of the 'mixed material' formed upon bombardment of bulk Be with energetic (keV) nitrogen ions. The formation of beryllium nitride within the implantation zone of a few nanometres is observed by x-ray photoelectron spectroscopy and Rutherford backscattering spectrometry. Upon implantation of N at 1.5 keV per atom, saturation of the Be surface with N occurs at a fluence of 2 × 1018 N cm−2 and a retained areal density of approximately 4 × 1016 N cm−2. The nitride undergoes an ordering process upon annealing, but does not decompose at temperatures up to 1000 K. The influence of such nitride layers on the retention and release of D implanted with different fluences is investigated by nuclear reaction analysis and temperature-programmed desorption. The nitride layer does not act as a diffusion barrier for out-diffusing hydrogen isotopes. A partial sputter yield of 0.013 N/D as a lower limit is measured upon bombardment of the nitride layer with D at 2 keV. These erosion measurements are influenced by the strong tendency of the nitride to oxidize.

Beryllium nitride thin films were grown on silicon substrates by laser ablating a beryllium foil in molecular nitrogen ambient. The composition and chemical state were determined with Auger (AES), X-Ray photoelectron (XPS) and energy loss (EELS) spectroscopies. A low absorption coefficient in the visible region, and an optical bandgap of 3.8 eV, determined by reflectance ellipsometry, were obtained for films grown at nitrogen pressures higher than 25 mTorr. The results show that the reaction of beryllium with nitrogen is very effective using this preparation method, producing high quality films., Comment: 13 pages, 5 figures. Submitted to Materials Letters

Thick-target yields for reactions of 3 He particles with B, N, Be and Na were determined by irradiating boron, beryllium nitride and sodium iodide with 3 He ions of energies from 6 to 18 MeV. Excitation functions for the reactions 11 B( 3 He, n) 13 N, 10 B( 3 He, d) 11 C, 14 N( 3 He, α) 13 N, 14 N( 3 He, d) 15 O, 9 Be( 3 He, n) 11 C and 23 Na( 3 He, 2p) 24 Na were obtained by numerical differentiation of the smoothed yield versus energy curves. The distorted-wave theory of nuclear reactions was used to compute excitation functions for comparison with the data for the 14 N( 3 He, α) 13 N reaction and for the ( 3 He, d) reactions on 14 N and 10 B. Optical-model potentials, not for the particular nucleides observed, but determined for neighbouring light nuclei, were used in the calculations. The results of this comparison of theory with experiment indicate that the 14 N( 3 He, α) and 10 B( 3 He, d) reactions appear to proceed mainly by direct pick-up and stripping processes, respectively. For the 14 N( 3 He, d) reaction, a stripping calculation that considered only those 15 O states with known spins and parities yielded a lower limit of ≈30% of the observed excitation function.

Calorimetric determinations of the heats of reaction of beryllium and of α- and β-beryllium nitride with chlorine enable the following heats of formation to be derived: ΔH°f298(α′-BeCl2)=–117.1±0.4 kcal/mole, ΔH°f298(α-Be3N2)=–141.0±1.6 kcal/mole, ΔH°f298(β-Be3N2)=–136.7±1.5 kcal/mole. A calorimetric determination of the heat of reaction of beryllium with ammonia gave a heat of formation of α-beryllium nitride, ΔH°f298(α-Be3N2)=–140.5±0.3 kcal/mole.

Excimer laser irradiation was used to induce rapid formation of nitride and oxide layers on beryllium samples immersed in liquid nitrogen and water, respectively. The elemental composition of the irradiated surfaces was determined by means of Rutherford backscattering spectrometry. Compound formation of Be3N2 and BeO was confirmed by x‐ray diffraction. The results show that extensive reaction occurred only if the laser energy was sufficient to melt the beryllium surface. The amount of incorporated nitrogen or oxygen atoms was initially proportional to the laser energy density and to the number of laser shots. Saturation occurred when a near stoichiometric layer of Be3N2 or BeO was formed at the surface. The rate of compound formation was extremely high, on the order of 10–100 nm per shot.

Excimer laser induced rapid formation of nitride and oxide layers on beryllium samples immersed in liquid nitrogen and water, resp., has been studied. From Rutherford backscattering spectra the amounts of incorporated nitrogen and oxygen were determined. In addition, scanning electron microscopy was used to study the morphology of the irradiated surface and compound formation was confirmed by X-ray diffraction. Our results show that extremely rapid reaction takes place when the laser energy is sufficient to melt the beryllium surface. The amount of reaction is found to be proportional to both the energy density and the number of laser shots, until a nearly stoichiometric layer of Be3N2 or BeO is formed at the surface, at which point the reaction saturates. Growth rates on the order 20 nm per shot are deduced from the data, which is orders of magnitude higher than those achieved by conventional means.

Methods for the recovery of C/sup 14/ from neutron-irradiated Re/sub 3/N/ sub 2/, based on solution in acid and alkali. are outlined. (C.J.G.)

The valence band density of states of bulk beryllium nitride (alpha-Be3N2) and the solvation energy of hydrogen atoms in this nitride is herein studied using the generalized gradient approximation density functional theory. The DOS is compared to photoelectron spectroscopy investigations of nitrogen-implanted beryllium. The presence of defects (atomic vacancies) was taken into consideration in the calculations on the trapping of deuterium. The barriers of activation for hydrogen atom diffusion in the bulk and from the defect were calculated and compared to their values in pure beryllium metal and in beryllium oxide. Some consequences regarding the effects of nitrogenation of beryllium as a plasma-facing material in nuclear fusion devices are eventually proposed.

The nature of the radioactive compounds formed in the production of C14 by neutron irradiation of beryllium nitride has been investigated. Solution of the irradiated powder gave activities corresponding to methane, carbon monoxide, carbon dioxide, hydrogen cyanide, methanol, and formic acid. Formaldehyde was not found. The distribution of activities is not affected by the acidity of the solvent. The results are considered in the light of earlier work.

The relative enthalpy of a sample of alpha beryllium nitride, Be(3)N(2), of 95 percent purity was precisely measured over the temperature range 273 to 1173 K using a drop calorimetric method. Corrections were applied for the impurities, and the resulting heat capacity-temperature function was required to join smoothly that from recent precise NBS adiabatic calorimetry which covered the range 20 to 315 K. The enthalpy, heat capacity, entropy, and Gibbs free-energy function were computed from empirical functions of temperature and tabulated from 273 to 1200 K.

The heat capacity of α-beryllium nitride. Be(3)N(2), was determined from 20 to 315 K and the thermodynamic properties calculated from 0 to 315 K. The entropy at 298.15 K was found to be 34.4 ±0.3 J/K· mol (8.23 ±0.08 cal/K· mol). The precision using a calorimeter of a new design is shown to be ± 0.01 percent over most of the temperature range of the measurements.

ALUMINIUM nitride activated by silicon1, and boron nitride activated by carbon2, are the only known phosphorescent nitrides.