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The structural, elastic, electronic, and magnetic properties of the CrCoSi, MnCoSi parent half-Heusler (HH) alloys, and their CrMn[Co.sub.2][Si.sub.2] derivative double half-Heusler (DHH) compound are studied, utilizing the augmented plane wave method, which is based on density functional theory and implemented in the WIEN2k code. The stability of HH structure of the CrCoSi and MnCoSi alloys has been checked for their non-magnetic and ferromagnetic phases, leading to that the latter phase of the type I arrangement is the most stable. The CrMn[Co.sub.2][Si.sub.2] DHH alloy, derivative from the found structural and magnetic ground states of CrCoSi and MnCoSi HH alloys, is constructed and investigated. This DDH as well as its CrCoSi parent HH are found to be resistant to deformation and can be classified as ductile materials, whereas the MnCoSi compound is brittle. By the gradient generalized approximation (GGA), the electronic structures of CrCoSi, MnCoSi, and CrMn[Co.sub.2][Si.sub.2]compounds exhibit a metallic behavior in the spin-up channel and a semiconducting behavior in the spin-dn channel, with band gaps (half-metallic gaps) of 0. 851(0.020), 0.852(0.021), and 0.531(0.002) eV, respectively. The half-metallicity of CrMn[Co.sub.2][Si.sub.2] DHH is retained with smaller (larger) band gap (half-metallic gap) of 0.38(0.106) eV than that of GGA, using GGA + U approximation. In addition, the total magnetic moments are found to be 1, 2, and 3 [[mu].sub.B] for CrCoSi, MnCoSi, and CrMn[Co.sub.2][Si.sub.2], respectively. Therefore, these alloys can be good candidates for spinitronic applications due to their half-metallicity. Key words: half-metal, heusler alloys, spin polarization, mechanical stability, FP-LAPW, 1. Introduction Spin-based electronics has grown into a significant field of study that spans a wide range of high spin-polarized materials, used in spintronic devices. It overcomes the limitations of [...]

In this work, a comprehensive investigation of the salicylideneaniline derivatives is carried out using density functional theory to determine their linear and nonlinear optical (NLO) properties. Geometry optimizations, for gas and solvent phases, of the tautomers (enol and keto forms) are calculated using B3LYP levels with 6-31G(d,p) basis set. An intramolecular proton transfer, for 1SA-E and 2SA-E, is performed by a PES scan process at the B3LYP/6-31G(d,p) level. The optical properties are determined and show that they have extremely high NLO properties. In addition, the RDG analysis, molecular electrostatic potential (MEP), and gap energy are calculated. The low energy gap value indicates the possibility of intramolecular charge transfer. The frontier molecular orbital calculations clearly show the inverse relationship of HOMO-LUMO gap with the first-order hyperpolarizability ([beta] = 59.6471 * [10.sup.-30] esu), confirming that the salicylideneaniline derivatives can be used as attractive future NLO materials. Therefore, the reactive sites are predicted using MEP and the visible absorption maxima are analyzed using a theoretical UV-Vis spectrum. Natural bond orbitals are used to investigate the stability, charge delocalization, and intramolecular hydrogen bond. Key words: first hyper polarizability, HOMO-LUMO energy gap, NLO properties, UV-Vis spectrum, tautomers. Nous completons ici une investigation des derives de salicylideneaniline en utilisant la theorie de la fonctionnelle de densite, afin de determiner leurs proprietes optiques lineaires et non lineaires. Nous calculons l'optimisation geometrique des tautomeres (dans les formes eno (eno) et ceto (keto)), pour les phases gazeuse et solute, en utilisant les niveaux B3YLP et l'ensemble de base 6-31G(d,p). Un transfert intramoleculaire, pour 1SA-E et 2SA-E, est verifie par balayage de l'energie potentielle de surface (EPS/PES) au niveau B3LYP/6-3G(d,p). Nous determinons les proprietes optiques des echantillons et montrons qu'elles sont extremement non lineaires. De plus, l'analyse du Gradient de Densite Reduite (GDR/RDG), le potentiel electrostatique moleculaire (PEM/MEP) et le gap d'energie sont aussi evalues. La faible valeur du gap d'energie indique la possibilite d'un transfert de charge intramoleculaire. Le calcul de l'orbitale moleculaire frontiere montre clairement l'inversion du gap HOMO-LUMO avec une hyperpolarisabilite ([beta] = 59.6471 * [10.sup.-30] esu), confirmant que les derives de salicylideneaniline peuvent etre utilises comme d'interessants materiaux en optique non lineaire (ONL/NLO). Par consequent, nous identifions les sites reactifs en utilisant le PEM et les maxima d'absorption dans le visible sont analyses via le spectre theorique UV-Vis. Les orbitales liees localisees (naturelles) sont utilisees pour analyser la stabilite, la delocalisation de charge et le lien hydrogene intramoleculaire. Mots-cles : premiere super polarisabilite, gap d'energie HOMO-LUMO, proprietes d'optique non lineaire, spectre UV-Vis, tautomeres., 1. Introduction Salicylideneaniline derivatives are of great interest due to the formation of O-H ... N (phenol-imine) and O ... H-N (keto-amine) type hydrogen bonds, which result in tautomerization between [...]

The structural, elastic, electronic, and magnetic properties of the CrCoSi, MnCoSi parent half-Heusler (HH) alloys, and their CrMnCo2Si2 derivative double half-Heusler (DHH) compound are studied, utilizing the augmented plane wave method, which is based on density functional theory and implemented in the WIEN2k code. The stability of HH structure of the CrCoSi and MnCoSi alloys has been checked for their non-magnetic and ferromagnetic phases, leading to that the latter phase of the type I arrangement is the most stable. The CrMnCo2Si2 DHH alloy, derivative from the found structural and magnetic ground states of CrCoSi and MnCoSi HH alloys, is constructed and investigated. This DDH as well as its CrCoSi parent HH are found to be resistant to deformation and can be classified as ductile materials, whereas the MnCoSi compound is brittle. By the gradient generalized approximation (GGA), the electronic structures of CrCoSi, MnCoSi, and CrMnCo2Si2compounds exhibit a metallic behavior in the spin-up channel and a semiconducting behavior in the spin-dn channel, with band gaps (half-metallic gaps) of 0.851(0.020), 0.852(0.021), and 0.531(0.002) eV, respectively. The half-metallicity of CrMnCo2Si2 DHH is retained with smaller (larger) band gap (half-metallic gap) of 0.38(0.106) eV than that of GGA, using GGA + U approximation. In addition, the total magnetic moments are found to be 1, 2, and 3 µB for CrCoSi, MnCoSi, and CrMnCo2Si2, respectively. Therefore, these alloys can be good candidates for spinitronic applications due to their half-metallicity. [ABSTRACT FROM AUTHOR]

The structural, elastic, electronic, and magnetic properties of the CrCoSi, MnCoSi parent half-Heusler (HH) alloys, and their CrMnCo2Si2 derivative double half-Heusler (DHH) compound are studied, utilizing the augmented plane wave method, which is based on density functional theory and implemented in the WIEN2k code. The stability of HH structure of the CrCoSi and MnCoSi alloys has been checked for their non-magnetic and ferromagnetic phases, leading to that the latter phase of the type I arrangement is the most stable. The CrMnCo2Si2 DHH alloy, derivative from the found structural and magnetic ground states of CrCoSi and MnCoSi HH alloys, is constructed and investigated. This DDH as well as its CrCoSi parent HH are found to be resistant to deformation and can be classified as ductile materials, whereas the MnCoSi compound is brittle. By the gradient generalized approximation (GGA), the electronic structures of CrCoSi, MnCoSi, and CrMnCo2Si2compounds exhibit a metallic behavior in the spin-up channel and a semiconducting behavior in the spin-dn channel, with band gaps (half-metallic gaps) of 0.851(0.020), 0.852(0.021), and 0.531(0.002) eV, respectively. The half-metallicity of CrMnCo2Si2 DHH is retained with smaller (larger) band gap (half-metallic gap) of 0.38(0.106) eV than that of GGA, using GGA + U approximation. In addition, the total magnetic moments are found to be 1, 2, and 3 µB for CrCoSi, MnCoSi, and CrMnCo2Si2, respectively. Therefore, these alloys can be good candidates for spinitronic applications due to their half-metallicity. [ABSTRACT FROM AUTHOR]