The structural, electronic and optical properties of CdxZn1 − xSe ternary alloys

The structural, electronic, and optical properties of Cd_xZn_1 − xSe alloys are investigated using the first-principles plane-wave pseudopotential method within the LDA approximations. In particular, the lattice constant, bulk modulus, electronic band structures, density of state, and optical properties such as dielectric functions, refractive index, extinction coefficient and energy loss function are calculated and discussed. Our results agree well with the available data in the literature.     

Regional characteristics of ultrasonic structural scattering in liver

I.IntroductionInrecentyears,manyhomeandabroadscholarshavedoneagreatdealofstudiesontissuecharacterizationusingacousticparametersincludingultrasonicattenuationcoefficient,scatteringcoefficiellt,andnonlinearparameterB/Aofbiologicaltissue.Theseresearcheshavelearntmuchknowledgeoftheacousticpropertiesofsofttissue.Butbecauseofthedifferenceinresearchmethodsandtestingconditions,thediscrepa-nceofmeasuredresultsisstilllargeandnosteadycharacterizationmodelcanbeformed-Atthesametime,thestudyofrevealingthe…     

Modular Irreducible Representations of Weyl Groups of Type B n

In this article, we build all the irreducible representations of a Weyl group of type B _n over a field of characteristic p > 2. This construction is based on [2 Aguado , J. , Araujo , J. ( 1998 ). Representations of the symmetric group 𝔖 _n on K[x ₁,…, x _n ] . Revista de la Unión Matemática Argentina 41 . [Google Scholar]], and in fact it extends the results of that article for the modular irreducible representations of the symmetric group.     

The stabilities, electronic structures and elastic properties of Rbben As systems

The structural, electronic and elastic properties of Rb-As systems (RbAs in NaP, LiAs and AuCu structures, RbAs₂ in the MgCu₂ structure, Rb₃As in Na₃As, Cu₃P and Li₃Bi structures, and Rb₅As₄ in the A₅B₄ structure) are investigated with the generalized gradient approximation in the frame of density functional theory. The lattice parameters, cohesive energies, formation energies, bulk moduli and the first derivatives of the bulk moduli (to fit Murnaghan's equation of state) of the considered structures are calculated and reasonable agreement is obtained. In addition, the phase transition pressures are also predicted. The electronic band structures, the partial densities of states corresponding to the band structures and the charge density distributions are presented and analysed. The second-order elastic constants based on the stress-strain method and other related quantities such as Young's modulus, the shear modulus, Poisson's ratio, sound velocities, the Debye temperature and shear anisotropy factors are also estimated.     

The stabilities, electronic structures and elastic properties of Rb-As systems

The structural, electronic and elastic properties of Rb–As systems (RbAs in NaP, LiAs and AuCu structures, RbAs2 in the MgCu2 structure, Rb3 As in Na3As, Cu3 P and Li3Bi structures, and Rb5 As4 in the A5B4 structure) are investigated with the generalized gradient approximation in the frame of density functional theory. The lattice parameters, cohesive energies, formation energies, bulk moduli and the first derivatives of the bulk moduli (to fit Murnaghan’s equation of state) of the considered structures are calculated and reasonable agreement is obtained. In addition, the phase transition pressures are also predicted. The electronic band structures, the partial densities of states corresponding to the band structures and the charge density distributions are presented and analysed. The second-order elastic constants based on the stress-strain method and other related quantities such as Young’s modulus, the shear modulus, Poisson’s ratio, sound velocities, the Debye temperature and shear anisotropy factors are also estimated.     

A molecular dynamics study on iridium

In this study, molecular dynamics simulations are performed by using a modified form of Morse potential function in the framework of the Embedded Atom Method (EAM). Temperature-and pressure-dependent behaviours of bulk modulus, second-order elastic constants (SOEC), and the linear-thermal expansion coefficient is calculated and compared with the available experimental data. The melting temperature is estimated from 3 different plots. The obtained results are in agreement with the available experimental findings for iridium.      

The first principles study on the Boron antimony compound

We present the results of our calculations on Boron antimony (BSb) compound in zinc-blende (ZB) and rock-salt (RS) structures by performing ab initio calculations within the local density approximation (LDA). Some basic physical properties, such as lattice constant, bulk modulus, cohesive energy, phase transition pressure, second-order elastic constants (C_ij), phonon frequencies, and some band structural parameters are calculated and compared with those obtained with other recent theoretical works. In order to further understand the behaviour of BSb compound, we have also predicted, the pressure-dependent behaviours of the band gap, second-order elastic constants (C_ij), Young's modulus, poison ratios (ν), Anizotropy factor (A), sound velocities, and Debye temperature for this hypothetical compound.     

Lattice vibrational properties of Al2X (X = Sc,Y) from density functional theory calculations

The phonon dispersion curves of the C15-type of Al₂Sc and Al₂Y compounds are investigated, using density functional theory within the generalized gradient approximation (GGA), based on the “direct method”. The obtained results show that both compounds are dynamically stable. The temperature dependence of the various thermodynamical quantities such as internal energy, free energy, entropy, and heat capacity are also predicted under the harmonic approximation, and the observed trends are discussed in detail.     

First principles study on the structural, electronic, and elastic properties of Na-As systems

We have performed the first principles calculation by using the plane-wave pseudopotential approach with the generalized gradient approximation for investigating the structural, electronic, and elastic properties Na-As systems (NaAs in NaP, LiAs and AuCu-type structures, NaAs₂ in MgCu₂-type structure, Na₃As in Na₃As, Cu₃P and Li₃Bi-type structures, and Na₅As₄ in A₅B₄-type structure). The lattice parameters, cohesive energy, formation energy, bulk modulus, and the first derivative of bulk modulus (to fit to Murnaghan’s equation of state) of the related structures are calculated. The second-order elastic constants and the other related quantities such as Young’s modulus, shear modulus, Poisson’s ratio, sound velocities, and Debye temperature are also estimated.     

Theoretical predictions of the structural,mechanical and lattice dynamical properties of XW2 (X = Zr,Hf) Laves phases

We have investigated the structural, mechanical and lattice dynamical properties of ZrW₂ and HfW₂ compounds in cubic C15 (space group Fd-3m), hexagonal C14 (space group P6₃/mmc) and C36 (space group P6₃/mmc) phases using generalized gradient approximation within the plane-wave pseudo-potential density functional theory. We have found that ZrW₂ and HfW₂ in cubic C15 phase are the most stable among the considered phases. From calculated elastic constants, it is shown that all phases are mechanically stable according to the elastic stability criteria. The related mechanical properties, such as bulk, shear and Young moduli, Poisson’s ratio, Debye temperature and hardness have been also calculated. The results show that ZrW₂ and HfW₂ compounds are ductile in nature with respect to the B/G and Cauchy pressure analysis. The phonon dispersion curves, phonon density of states and some thermodynamic properties are computed and discussed exhaustively for considered phases.