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The structural, dynamical, elastic, electronic, optical, and thermodynamic properties for the [Na.sub.2]ZnSn[S.sub.4] compound is reported using the density functional theory in the framework of the full-potential linearized augmented plane wave method within the Wu and Cohen generalized gradient and Tran-Blaha modified Becke-Johnson approaches. Calculations shows that [Na.sub.2]ZnSn[S.sub.4] is more stable in the kesterite phase. Phonon studies indicate that this compound is dynamically stable. The elastic constants are calculated and used to confirm the mechanical stability. Moreover, our compound is thermodynamically stable and the conditions of Sn-rich/Na-poor are necessary to form a single-phase [Na.sub.2]ZnSn[S.sub.4] crystal. The shear modulus, Young's modulus, Poisson's ratio, anisotropy factor, Lame's constant, and Pugh indicator have also been calculated. The electronic properties shows that [Na.sub.2]ZnSn[S.sub.4] has a direct gap ([GAMMA]-[GAMMA]) of 3.18 eV. The optical properties suggests that [Na.sub.2]ZnSn[S.sub.4] is a good candidate for nonlinear optical applications. The thermodynamic properties such as Debye temperature, thermal expansion coefficient, heat capacities, and entropy are also estimated under temperature and pressure effects. Key words: quaternary chalcogenide semiconductor, FP-LAPW, electronic properties, optical properties Les proprietes structurelles, dynamiques, elastiques, electroniques, optiques et thermodynamiques du compose [Na.sub.2]ZnSn[S.sub.4] sont calcules a l'aide de la theorie de la fonctionnelle de la densite (TFD/DFT) dans le cadre de la methode d'onde plane augmentee linearisee a potentiel complet (OPAL-PC/FP-LAPW) en utilisant l'approximation du gradient generalise de Wu et Cohen (MGG-WC/GGA-WC) et l'approche de Becke-Johnson modifiee par Tran-Blaha. Les calculs montre que [Na.sub.2]ZnSn[S.sub.4] est plus stable dans la phase Kesterite. Les etudes sur phonons indiquent que ce compose est dynamiquement stable. Les constantes elastiques sont calculees et utilisees pour confirmer la stabilite mecanique. De plus, notre compose est thermodynamiquement stable et que les conditions Sn-riche/Na-pauvre sont necessaires pour former un cristal [Na.sub.2]ZnSn[S.sub.4] monophase. Le module de cisaillement, le module de Young, le rapport de Poisson, le facteur d'anisotropie, la constante de Lame et l'indicateur de Pugh ont egalement ete calcules. Les proprietes electroniques montre que [Na.sub.2]ZnSn[S.sub.4] a un gap direct (r-r) de 3.18 eV. Les proprietes optiques suggere que ce compose est un bon candidat pour des applications en optique non lineaire. Les proprietes thermodynamiques tells que la temperature de Debye, le coefficient d'expansion thermique, les capacites thermiques et l'entropie l'entropie sont egalement estimees sous les effets de la temperature et de la pression. Mots-cles : semiconducteur de chalcogenure quaternaire, OPAL-PC/FP-LAPW, proprietes electroniques, proprietes optiques, 1. Introduction Research in the physics of materials has greatly contributed to the emergence and development of recent new technologies such as spintronics, photovoltaics, and nonlinear optics (NLO). It must [...]

In this paper, we studied the magnetic stability, structural, elastic and electronic properties of Ir2FeAl full Heusler compound in the regular phase (Cu2MnAl, prototype L2 1) , by using the first principle of density functional theory, with the generalized approximation of the GGA gradient. We found that the ferromagnetic state of Ir2FeAl is more stable than the nonmagnetic configuration at their lattice parameters equilibrium. This result was confirmed by the calculation of the cohesive energy. The stability is asserted by the elastic constants and the conditions of the mechanical stability criterion. The band structure and the calculated densities of states (DOS) of this alloy show a semi-metallic behavior. The ferromagnetic performance of Ir2FeAl is confirmed by the total magnetic moment of 4.28 μ B , where its major contribution comes from Fe atoms. We estimated the Debye temperature of Ir2FeAl from the average speed of sound. This is the first quantitative theoretical prediction of the elastic properties of the Ir2FeAl compound, and it still awaits experimental confirmation. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) calculations have been performed to obtain optimized geometries, highest occupied molecular orbital (HOMO)--lowest unoccupied molecular orbital (LUMO) energies, nonlinear optical (NLO), and thermodynamic properties for N-(3-methylphenyl)-2-nitrobenzene-sulfonamide of formula [C.sub.13][H.sub.12][N.sub.2][O.sub.4]S in different solvents. B3LYP level gives similar results for geometric parameters. The most stable structure, which is defined by the highest energy gap between HOMO and LUMO, is obtained in gas phase ([DELTA]E = 3.815888 eV), Obtained small energy gaps between HOMO and LUMO demonstrate the high-charge mobility in the titled compound. The magnitude of first static hyperpolarizability ([beta]) parameter increases by the decreasing HOMO-LUMO energy gap. The intensive interactions between bonding and antibonding orbitals of titled compound are responsible for movement of [pi]-electron cloud from donor to acceptor, that is, intramolecular charge transfer, inducing the nonlinear optical properties. So, the [beta] parameter for title compound is found to be in the range of 5.10598-9.03 063 x [10.sup.-30] esu, indicating the considerable NLO character. All of these calculations have been performed in gas phase as well as water and ethanol solvents in order to demonstrate solvent effect on molecular structure, vibration frequencies, NLO properties, etc. Key words: DFT, NBO, HOMO-LUMO, IR spectra, NLO. Des calculs de theorie de la fonctionnelle de la densite (DFT) ont ete effectues pour obtenir des geometries optimisees, les energies orbitales moleculaires occupees les plus basses (HOMO), les energies des orbitales moleculaires inoccupee les plus basses (LUMO), les proprietes optiques non-lineaires (NLO) et les proprietes thermodynamiques pour le N-(3-methylphenyl)-2-nitrobenzene-sulfonamide de formule brute [C.sub.13][H.sub.12][N.sub.2][O.sub.4]S dans differents solvants. Le niveau de B3LYP donne des resultats similaires pour les parametres geometriques et les frequences de vibration en phase gazeuse, eau et ethanol. La structure la plus stable, definie par le plus grand gap energetique entre HOMO et LUMO, est obtenue en phase gazeuse ([DELTA]E = 3,815888 eV), L'obtention de gaps energetiques entre HOMO et LUMO demontrent la mobilite a charge elevee dans le compose etudie. L'amplitude du premier parametre d'hyperpolarisabilite statique ([beta]) augmente avec le decroissement du gap energetique HOMO-LUMO. Les interactions intensives entre les orbitales liantes et les orbitales antiliantes du compose etudie sont responsables du mouvement du nuage d'electrons [pi] du donneur a l'accepteur, c'est-a-dire le transfert de charge intramoleculaire (TIC), induisant les proprietes optiques non lineaires. Ainsi, le parametre [beta] pour le compose se trouve dans la gamme de 5,10598-9,03063 x [10.sup.-30] esu, indiquant le caractere NLO considerable. Tous les calculs ont ete effectues dans la phase gazeuse aussi bien que dans le solvant (l'eau et l'ethanol) afin de demontrer l'effet de solvant sur la structure moleculaire, les frequences de vibration et les proprietes NLO, etc. Mots-cles : DFT, NBO, HOMO-LUMO, IR spectra, NLO., 1. Introduction Le N-(3-methylphenyl)-2-nitrobenzene-sulfonamide [1] fait partie de la famille des sulfonamides qui forment une classe importante de composes en chimie medicinale et pharmaceutique avec plusieurs applications biologiques [2-5]. Beaucoup [...]

Using the first-principle methods based on the density functional theory, in order to study structural, elastic, and electronic properties of MAX phases M 2 CdC with M = (Sc, V, and Nb). The calculated formation energies revealed that these compounds are thermodynamically stable in the hexagonal MAX phase. The stability is affirmed by the elastic constants and the conditions of the mechanical stability criterion. The calculated electron band structures and the density of states imply that the chemical bond in three compounds are a combination of covalent, ionic, and metallic nature. The main factors governing the electronic properties are the hybrid states M-d, Cd-p, and C-p, and the bond (p-d) stabilizes the structure. Fermi's surface characteristics have been studied for the first time. Based on the total energy, we conclude that as continue to increase Sc-V, Nb, the compressibility modulus decreases. At the same time, it gives a stabilization of the hexagonal structure and increases the metal support. [ABSTRACT FROM AUTHOR]

In this paper, the structural, electronic, magnetic, and half-metallic properties of full-Heusler alloys Mn2ZrX (X = As , Bi) in the Hg2CuTi-type structure have been studied by using the first-principles-based density functional theory (DFT) with the full-potential linearized augmented plane-wave (FP-LAPW) method. Mn2ZrX (X = As , Bi) compounds are found to be half-metallic ferrimagnets. The calculated total magnetic moments of the Mn2ZrX (X = As , Bi) alloys are estimated at 01 μ B according to the Slater–Pauling rule of M tot = ( Z tot –24) μ B . It was discovered that Mn2ZrAs and Mn2ZrBi maintained their half-metallicity for a lattice constant interval of 5.72 to 6.26 Å and 6.33 to 6.62 Å, respectively, and present a maximum degree of spin polarization at the Fermi level. In addition, the predicted formation energy and elastic parameters show that these materials are mechanically stable. All of these results indicate that these new Mn2-based heusler alloys are able to be the candidates for spintronic applications. [ABSTRACT FROM AUTHOR]

The structural, dynamical, elastic, electronic, optical, and thermodynamic properties for the Na2ZnSnS4 compound is reported using the density functional theory in the framework of the full-potential linearized augmented plane wave method within the Wu and Cohen generalized gradient and Tran–Blaha modified Becke–Johnson approaches. Calculations shows that Na2ZnSnS4 is more stable in the kesterite phase. Phonon studies indicate that this compound is dynamically stable. The elastic constants are calculated and used to confirm the mechanical stability. Moreover, our compound is thermodynamically stable and the conditions of Sn-rich/Na-poor are necessary to form a single-phase Na2ZnSnS4 crystal. The shear modulus, Young's modulus, Poisson's ratio, anisotropy factor, Lamé's constant, and Pugh indicator have also been calculated. The electronic properties shows that Na2ZnSnS4 has a direct gap (Γ–Γ) of 3.18 eV. The optical properties suggests that Na2ZnSnS4 is a good candidate for nonlinear optical applications. The thermodynamic properties such as Debye temperature, thermal expansion coefficient, heat capacities, and entropy are also estimated under temperature and pressure effects. [ABSTRACT FROM AUTHOR]

We use the first-principles-based density functional theory with full potential linearized augmented plane wave method to investigate the structural, elastic, electronic, and thermoelectric properties of ZrIrAs, ZrIrBi, and ZrIrSb. The calculated structural and elastic constants with generalized gradient potential developed by Perdew-Burke-Ernzerhof (GGA-PBEsol) reveal that our compounds are stable in the cubic LiAlSi-type structure. The electronic structures are calculated with GGA-PBEsol and improved by Tran-Blaha modified Becke-Johnson (TB-mBJ) potential. The thermoelectric properties were determined at temperatures of 300, 600, and 800 K with respect to the p-type and n-type doping levels. We find that the thermopower factors are larger for p-type doping, implying that the hole doping provides more enhancement of thermoelectric performances in ZrIrAs, ZrIrBi, and ZrIrSb. Among them, the best thermopower values were found for the ZrIrAs compound with optimal doping levels of 46.17, 133.05, and 185.92 $$\times 1014\,\upmu \hbox {W}\, \mathrm{cm}^{-1}\; \hbox {K}^{-2}\;\hbox {s}^{-1}$$ at temperatures of 300, 600, and 800 K, respectively. [ABSTRACT FROM AUTHOR]

We present a quantum-mechanical first-principle calculation of the structural, elastic, electronic, and magnetic properties of the full-Heusler compounds TiNi X ( X= Al, Ga, and In). The calculation uses the full-potential linearized augmented plane waves plus local orbital method to describe Ti-based Heusler alloys. The results show that these compounds exhibit half metallic characteristics over a wide range of mesh parameters and obey the Slater-Pauling rule, which states that the total magnetic moment per unit cell M = Z − 18 for half-Heusler compounds XYZ and M = Z − 24 for full-Heusler X YZ compounds. For these new alloys TiNi X ( X= Al, Ga, and In), we initially considered the two possible L2 structures AlCuMn and CuHgTi. However, two subsequent structural studies showed that only the CuHgTi-like structure is half metallic. Over a wide range of mesh parameters, the calculations give a total magnetic moment of 3.00 μ . These results suggest that TiNi X ( X= Al, Ga, and In) are promising materials for spintronic applications. [ABSTRACT FROM AUTHOR]

The structural, elastic, electronic and magnetic properties of the MnRhSi Mn-based Heusler alloy were investigated by using first-principles calculations of the full-potential linearized augmented plane wave (FP-LAPW) method. The results of electronic structures show that the MnRhSi exhibits a half-metallic character for a wide range 5.65 to 5.91 Å of lattice constant. The half-metallic behavior is confirmed by the integral value of 3 μ of the total magnetic moment for MnRhSi, which follow the Slater-Pauling rule. [ABSTRACT FROM AUTHOR]