Zinc-blende BN Research Articles

Electronic and elastic properties of BN, AlN and GaN

We have carried out first-principles total energy calculations to investigate electronic and elastic properties of both zinc-blende and wurtzite BN, AlN, and GaN. We have calculated lattice parameters, elastic constants, deformation potential constants, phonon frequencies at r point, Born effective charges, and piezoelectric constants. Lattice parameters are fully relaxed by using the first-principles molecular dynamics method with variable cell shape. The internal strain in a strained crystal is also relaxed by the first-principles molecular dynamics method. The internal strain influences the elastic constants, the deformation potential constants, and the piezoelectric constants effectively. We have calculated the wurtzite deformation potential constants D1 – D5 considering the internal strain correction. The piezoelectric constants of wurtzite and also zinc-blende crystals have been calculated using the Berry phase approach and we have found from first principles that those of BN have an inverse sign in contrast to AlN and GaN. Discussions will be given in comparison with results obtained herein with the previous ones. © 1998 American Institute of Physics. [S0021-8979(98)07921-3]

Electronic and elastic properties of BN, AlN and GaN

We have carried out first-principles total energy calculations to investigate electronic and elastic properties of both zinc-blende and wurtzite BN, AlN, and GaN. We have calculated lattice parameters, elastic constants, deformation potential constants, phonon frequencies at r point, Born effective charges, and piezoelectric constants. Lattice parameters are fully relaxed by using the first-principles molecular dynamics method with variable cell shape. The internal strain in a strained crystal is also relaxed by the first-principles molecular dynamics method. The internal strain influences the elastic constants, the deformation potential constants, and the piezoelectric constants effectively. We have calculated the wurtzite deformation potential constants D1 – D5 considering the internal strain correction. The piezoelectric constants of wurtzite and also zinc-blende crystals have been calculated using the Berry phase approach and we have found from first principles that those of BN have an inverse sign in contrast to AlN and GaN. Discussions will be given in comparison with results obtained herein with the previous ones. © 1998 American Institute of Physics. [S0021-8979(98)07921-3]

Crystal structure of rare earth and group III nitride alloys by ab initio calculations

The ground state phases of ternary alloys of rare earth and group III nitride semiconductors have been investigated within the density functional theory. The most energetically favorable crystal phases among possible cubic and hexagonal structures, i.e., the rock salt, zinc blende, wurtzite, and hexagonal BN, were determined. The type of a unit cell and the lattice parameters of the materials are presented as a function of their composition. Furthermore, effects of strain on ground states of group III and rare earth nitride materials are discussed. The findings presented in this work discloses the wurtzite type materials as being stable with relatively low contents of rare earth elements. It is expected that the wurtzite phase will be very persistent only in the La-based systems. Nevertheless, the two-dimensional hexagonal atomic layers are revealed as being a metastable phase for all alloys studied. This finding supports the conclusion of previous experimental reports for Sc-doped GaN systems that the presence of rare earth ions in group III nitride materials leads to flattening of the wurtzite type layers.

Thermodynamic functions for boron nitride with q-deformed exponential-type potential

Within the framework of the supersymmetric quantum mechanics, the energy spectrum of the six-parameter exponential-type potential model was obtained. The partition function for this energy has been calculated in a closed and compact form and was used to obtain an expression for the ro-vibrational mean free energy F(T), mean free energy U(T), entropy S(T), and the specific heat capacity C(T). The thermodynamic functions obtained were then applied to study the behaviour of the zinc-blende BN crystal structure and the results obtained show fair agreement with reported experimental data for the specific heat capacity.

Heat Capacity of BN and GaN binary semiconductor under high Pressure-Temperature (PT) from First-principles

In this paper, we have calculated the molar heat capacity for cubic zinc blende (cZB) BN and GaN binary semiconductors at high pressure-temperature (PT). For the calculation of heat capacity, we firstly obtained the Debye temperature (ϴD) variation with temperature and at higher temperature it becomes constant with temperature in quasi-harmonic approximation limits. We have also calculated the static Debye temperature (ϴD) from elastic constant for the both BN and GaN binary semiconductors. The elastic constants are calculated from the energy-strain relation using plane wave method in DFT approach. All the calculated

Hardness analysis of cubic metal mononitrides from first principles

Density functional theory calculations are performed to evaluate the hardness of various cubic metal nitrides: rocksalt TiN, VN, ZrN, NbN, AlN, and SiN; zincblende AlN and BN; and diamond C for comparison. The isotropic elastic stiffness constants ${c}_{ij}$, bulk modulus $K$, shear modulus $G$, Young's modulus $E$, and isotropic Poisson's ratio $\overline{\ensuremath{\nu}}$ are calculated. From simulated uniaxial stress-strain curves, ideal strength values ${\ensuremath{\sigma}}_{\mathrm{max}}$ in the [100], [110], and [111] directions are also evaluated for all systems. In particular, rocksalt AlN is found to possess both high elastic moduli and ideal strength. These quantities are then compared for correlations with existing experimental Vicker's hardness data. The bulk modulus is found to be a poor indicator of hardness, while $E$, $G$, $1/\overline{\ensuremath{\nu}}$, and ${\ensuremath{\sigma}}_{\mathrm{max}}$ all exhibit stronger correlations. With a view to circumvent the need to run computationally expensive relaxation steps, different methodologies for approximating uniaxial stress-strain curves are introduced. Utilizing the anisotropic Poisson's ratio to approximate the relaxed transverse lattice parameters at a given axial strain is a good approximation to stress-strain curves, and the ideal strengths obtained in this way exhibit strong correlations to experimental Vicker's hardness values.

Z-BN: a novel superhard boron nitride phase

A superhard boron nitride phase dubbed as Z-BN is proposed as a possible intermediate phase between h-BN and zinc blende BN (c-BN), and investigated using first-principles calculations within the framework of density functional theory. Although the structure of Z-BN is similar to that of bct-BN containing four-eight BN rings, it is more energetically favorable than bct-BN. Our study reveals that Z-BN, with a considerable structural stability and high density comparable to c-BN, is a transparent insulator with an indirect band gap of about 5.27 eV. Amazingly, its Vickers hardness is 55.88 GPa which is comparable to that of c-BN. This new BN phase may be produced in experiments through cold compressing AB stacking h-BN due to its low transition pressure point of 3.3 GPa.

Structural and electronic properties of zinc blende B xAl 1− xN yP 1− y quaternary alloys via first-principle calculations

The structural and electronic properties of cubic zinc blende BN, BP, AlN and AlP compounds and their B x Al 1− x N y P 1− y quaternary alloys, have been calculated using the non relativistic full-potential linearized-augmented plane wave FP-LAPW method. The exchange-correlation potential is treated with the local density approximation of Perdew and Wang (LDA-PW) as well as the generalized gradient approximation (GGA) of Perdew–Burke and Ernzerhof (GGA-PBE). The calculated structural properties of BN, BP, AlN and AlP compounds are in good agreement with the available experimental and theoretical data. A nonlinear variation of compositions x and y with the lattice constants, bulk modulus, direct and indirect band gaps is found. The calculated bowing of the fundamental band gaps is in good agreement with the available experimental and theoretical value. To our knowledge this is the first quantitative theoretical investigation on B x Al 1− x N y P 1− y quaternary alloy and still awaits experimental confirmations.

First-principles study of structural, elastic, electronic, lattice dynamic and optical properties of XN (X=Ga, Al and B) compounds under pressure

We have applied the pseudo-potential plane wave method to study the structural, elastic, electronic, lattice dynamic and optical properties of GaN and AlN in the wurtzite lattice and BN with zinc-blende structure. We have found that all elastic constants depend strongly on hydrostatic pressure, except for C44 in wurtzite AlN and GaN that shows a weaker dependence. AlN and GaN present a direct band gap Γ–Γ, whereas BN has an indirect band gap Γ–X. The indirect Γ–K band gap in AlN occurs at about 35 GPa. The top of the valence bands reflects the p electronic character for all structures. There is a gap between optical and acoustic modes only for wurtzite phases AlN and GaN. All peaks in the imaginary part of the dielectric function for the wurtzite lattice GaN and AlN move towards lower energies, while those in the zinc-blende BN structure shift towards higher energies with increasing pressure. The decrease of the static dielectric constant and static refractive index in zinc-blende BN is weaker and it can be explained by its higher elastic constants.

COMPARATIVE STUDY OF THE STRUCTURAL AND ELECTRONIC PROPERTIES OF BN(5, 5) AND C(5, 5) NANOTUBES UNDER PRESSURE

The structural and electronic properties of BN(5, 5) and C(5, 5) nanotubes under pressure are studied by using first principles calculations. In our study range, BN(5, 5) undergoes obvious elliptical distortion, while for C(5, 5) the cross section first becomes an ellipse and then, under further pressure, is flattened. The band gap of BN(5, 5) decreases with increasing pressure, which is inverse to that of zinc blende BN, whereas for C(5, 5) the metallicity is always preserved under high pressure. The population of charge density indicates that intertube bonding is formed under pressure. We also find that BN(5, 5) may collapse, and a new polymer material based on C(5, 5) is formed by applying pressure.

Correlation-induced corrections to the band structure of boron nitride: A wave-function-based approach

We present a systematic study of the correlation-induced corrections to the electronic band structure of zinc-blende BN. Our investigation employs an ab initio wave-function-based local Hamiltonian approach which offers a rigorous theoretical framework for the calculation of the polarization and local charge redistribution effects around an extra electron or hole placed into the conduction or valence bands of semiconducting and insulating materials. Moreover, electron correlations beyond relaxation and polarization can be readily incorporated. The electron correlation treatment is performed on finite clusters. In conducting our study, we make use of localized Wannier functions and embedding potentials derived explicitly from prior periodic Hartree-Fock calculations. The on-site and nearest-neighbor charge relaxations bring corrections of several eV to the Hartree-Fock band gap. Additional corrections are caused by long-range polarization effects. In contrast, the dispersion of the Hartree-Fock bands is marginally affected by electron correlations. Our final result for the fundamental gap of zinc-blende BN compares well with that derived from soft x-ray experiments at the B and N K-edges.

High-pressure lattice dynamics and thermodynamic properties of zinc-blende BN from first-principles calculation

The density function perturbation theory (DFPT) is employed to study the lattice dynamics and thermodynamic properties (with quasiharmonic approximation) of zinc-blende BN. First we discuss the structural properties and compare the phonon spectrum with available Raman scattering experiments. Thereafter using the calculated phonon dispersions we obtain the PTV equation of state from the free energy. Our results for the above properties are generally speaking in good agreement with experiments and with similar theoretical calculations. Owing to the anharmonic effect at high temperature, the calculated linear thermal expansion coefficients (CTE) are low to experimental data.

The dielectric and dynamical properties of zinc-blende BN, AlN and GaN from first-principle calculation

The ab initio calculations of the electronic structural, dielectric and lattice-dynamical properties of zinc-blende BN, AlN and GaN were presented. The ground-state properties, i.e., the lattice constant, the bulk modulus and band gap, were calculated using a plane-wave-pseudopotential method within the density-function theory. A linear-response approach to the density-function perturb theory was used to derive the Born effective charge, the high-frequency dielectric constants and interatomic force constants for these materials. The interatomic force contants (IFCs) are useful for interpolating the dynamical matrices through the whole Brillouin zone. Phonon frequencies along high-symmetry lines were also obtained by interpolating the dynamical matrices using the interatomic force constants. In this paper, we discussed the difference of dielectric and dynamical properties among zinc-blende BN, AlN and GaN, and meanwhile, also compared these properties with other experimental data available and theoretical values. Generally, the calculations were in good agreement with the other existing experimental data and theoretical values.

Anisotropic ideal strengths and chemical bonding of wurtzite BN in comparison to zincblende BN

The ideal strengths, electronic density of states, and charge density difference of wurtzite $w$-BN had been calculated by ab initio density functional theory and compared to zincblende $c$-BN. Both polymorphs show a different stacking of lattice planes but have comparable anisotropic strengths, which are due to the similar bonding of three-dimensional $s{p}^{3}$ covalent networks, comparable bond lengths, and charge transfer between the boron and nitrogen atoms.

Electronic structure of half-Heusler semiconductor LiBeN

A new cubic half-Heusler structure LiBeN can be derived from the zinc-blende BN, and has a similar band structure to BN. The structural, elastic properties and band structures of LiBeN and zinc-blende BN were studied using the full potential augmented plane wave plus local orbitals method within density functional theory. The conduction band modifications of LiBeN, compared to its zinc-blende analog BN, were discussed. For both BN and LiBeN, the valence band top is at the Γ point. For BN and α-LiBeN (Li+ near the anion), the conduction band minimum is at the X point. The β-LiBeN (Li+ near the cation) has the conduction band minimum at the L point, due to the increase (decrease) of conduction band bottom energy at X (L) point, relative to Γ point. The band gaps of LiBeN decrease compared to BN. The total energy calculations show the α phase to be more stable than the β phase for LiBeN.

Ab initio calculation of the structural and dynamical properties of the zinc-blende BN and its (110) surface

Using a first-principles pseudopotential technique, we have presented static and dynamical properties of cubic-BN. The calculated values for the lattice constant, bulk modulus, its first derivative and optical dielectric constant are in good agreement with available experimental and theoretical results. Phonon dispersion curves and density of states for cubic-BN were calculated by employing a density functional perturbation theory. In particular, the calculated zone-center and zone-edge phonons compare very well with available experimental results. The calculated structural parameters for the BN(110) surface are in good agreement with previous theoretical results. The highest surface optical phonon mode resonates with the bulk continuum along Γ¯– X¯′ (i.e. across the top-layer B–N atomic chain). Along other symmetry directions, this mode lies above the bulk continuum. The surface acoustic branches lie below the bulk continuum. Energy locations and polarization characteristics of surface rotational and bond stretching phonon modes have been determined.

First-principles studies on the pressure dependences of the stress–strain relationship andelastic stability of semiconductors

We investigate the stress–strain relationship and elastic stability of zinc-blende GaP, GaN,InP and BN lattices under hydrostatic pressure by first-principles calculation. A simpleand direct ab initio implementation for studying the mechanical properties ofcubic crystals is developed. The four phases’ full-set stress–strain coefficients inwide pressure ranges are theoretically calculated. The fundamental mechanism ofelastic stability and the origin of phase transformation under hydrostatic pressureare explored. We found that the abilities for most of these lattices are enhancedto sustain axial strain but weaken to shear strain under higher pressure. Theconditions of lattice stability are analysed using both the thermodynamic work–energycriterion and the elastic-stiffness criteria. We show that the lattice collapse ofthe perfect crystals is caused by the disappearance of their bulk moduli undervolume dilation. Lattice defects are considered to be the main reason causing phasetransformation under pressure. The correlation between the phonon softening and thevariation of elastic coefficients is studied. The pressure dependence of the Kleinmaninternal strain parameter and its relationship to elastic stability is also explored.

Prediction study of elastic properties under pressure effect for zincblende BN, AlN, GaN and InN

We have performed a first-principles full-potential augmented-plane wave plus local orbitals (FP-APW+lo) calculations with density functional theory in local density approximation, in aim to determine and predict the pressure dependence of elastic constants of BN, AlN, GaN and InN compounds. From our results, we sustain the idea of no evidence that the soft acoustic mode is responsible for the phase transition.

First principles calculations of the hypothetical interface BN/XC (X = Si, Ge, Sn)

The electronic structure and bonding configuration at the interface between cubic (zinc-blende) BN and XC (X = Si, Ge, Sn) are studied using the full-potential linearized augmented plane wave approach within the density functional theory in the local density approximation. The (001) superlattice of (BN) n/(XC) nis used to study the interface. The calculated results show that the preferred bonding configuration is X–N and C–B for the (001) BN/XC interface. The formation energy of the interface is studied as a function of thickness of the superlattice. The origin of the bonding formation as well as the electronic properties are also investigated.

Elastic, structural, bonding, and defect properties of zinc-blende BN, AlN, GaN, InN and their alloys

Simple tight-binding simulations, incorporating only the Herman–Skillman atomic term values, are shown to provide valuable information about the bonding, elastic and structural properties of zinc-blende group III-nitrides. Our calculated values of the elastic parameters (viz., bulk modulus, elastic stiffness constants, Kleinman's internal displacement parameter, Keating force constants, etc.) for BN, AlN, GaN, and InN are shown to exist well within the range of values derived from more sophisticated methods. Despite the crude approximations used, the tight-binding method has clearly provided the meaningful trends to the local distortions around isoelectronic impurities and has described reasonably well the bond length variations as a function of composition in ternary alloys.