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Based on density functional theory, structural, electronic, magneto-optic, and thermoelectric properties of RbCaN₂ and RbCaO₂, Heuslerene compounds have been calculated. These compounds have the ground state points with total magnetic moment of 1.0${\mu }_B$, which represents their ferromagnetic behavior. The RbCaN₂ Heuslerene has the half-metallic nature and RbCaO₂ case is a magnetic semiconductor. The Kerr angle of the RbCaN₂ Heuslerene has two relatively peaks at the energies of 5.5eV to 7.0eV, but for the RbCaO₂ compound, this diagram is wider in a larger energy range. Faraday angle peaks occurred at 6.2eV and 6.8eV for RbCaN₂ and RbCaO₂ compounds, which indicates the polarization of the light irradiated to them at these energies. It was observed that both compounds show high thermoelectric quality at temperatures higher than the room-temperature, and both compounds are suitable for power generator applications.

In this paper, we report the optoelectronic, thermoelectric properties and dynamic stability under the pressure of LiGaC half-Heusler within the Density Functional Theory (DFT) and semi-classical Boltzmann Transport Theory (BTT). The obtained results of the ground state show that the compound is structural, chemical, mechanical and dynamically stable in type I structure and maintains its stability under pressure. The obtained electronic properties reveal that the compound has a semiconducting nature with an indirect bandgap and the bandgap values slightly increase with pressure increase. The optical properties such as real and imaginary parts of dielectric function, refractive index and extinction coefficient, reflectivity and absorption coefficient and optical conductivity are calculated and discussed. The highest peaks of reflectivity and absorption coefficient are found in the ultra-violet (UV) region, suggesting that the compound LiGaC has a high potential for use in UV optoelectronic applications. The thermoelectric properties are also calculated in the temperature range from 300K to 900K and pressure range from 0GPa to 40GPa. At 300K and for all pressures selected, the maximum value of figure of merit is close to unity. Finally, we could make our conclusion that LiGaC is well suitable for multiple optical and thermoelectric applications.

The mesogenic behavior and electronic properties of hydrogen bond ferroelectric liquid crystal (HBFLC) complex are studied using experimental and theoretical techniques. HBFLC complex is synthesized from mesogenic 4-hexyloxy benzoic acid (6O BA) as the proton donor and nonmesogenic chiral DL-tartaric acid (DLTA) as the proton acceptor through intermolecular hydrogen bonding. Molecular geometry of DLTA+6O BA HBFLC complex is optimized by density functional theory (DFT) calculation. An interesting observation is that polarizing optical microscope (POM) study confirms that the HBFLC complex exhibits thermochromic behavior in chiral nematic (N${}^{\ast })$ along with induced nontitled smectic G^* phases. Another noteworthy observation is the manifestation of tripartite temperature stages. Fourier-transform infrared spectroscopy (FTIR) and natural bond orbital (NBO) analysis elucidate the intermolecular hydrogen bond between mesogenic (6O BA) and nonmesogenic (DLTA) compounds. Further, frontier molecular orbital (FMO) study and electrostatic potential (ESP) analysis explore the reactivity sites, intermolecular charge transfer and electronic behavior of HBFLC complex.

This paper aims to investigate the behavior of LiMgN half-Heusler (HH) semiconductor doped by transition metals (TM $=$ Mn, Fe, Co and Ni). HHs belong to the $F\bar{4}3m$ space group (No. 216) and have a zinc blende structure that can be described by the chemical symbol XYZ. The research methodology utilized in this investigation involves theoretical analysis based on the principles of density functional theory (DFT). The studied LiMg${}_{0.95}$TM${}_{0.05}$N alloy displayed the half-metallicity behavior when TM $=$ Fe, Co and Ni. Hence, these systems could be a promising candidate in spintronic application thanks to their ferromagnetism. The principal contribution to magnetism in the full LiMg${}_{0.95}$TM${}_{0.05}$N alloys comes from the Mn, Fe, Co and Ni doping. The partial magnetic moments of these elements are significantly greater than the combined partial magnetic moments of Li, Mg and N. When comparing LiMg${}_{0.95}$Mn${}_{0.05}$N to LiMg${}_{0.95}$Fe${}_{0.05}$N, ₅Co${}_{0.05}$N and LiMg${}_{0.95}$Ni${}_{0.05}$N, it is important to note that the exchange splitting energy ${\mathrm{\Delta }}_{(e^{+},e^{-})}^{\mathrm{\text{TM}}}$ associated to their spin up and spin down were discussed. The variation of Mn(3d) in relation to ($e^{+},e^{-}$) is larger than that of Fe, Co and Ni. Therefore, ${\mathrm{\Delta }}_{(e^{+},e^{-})}^{\mathrm{\text{Mn}}}>{\mathrm{\Delta }}_{(e^{+},e^{-})}^{\mathrm{\text{Fe}}}>{\mathrm{\Delta }}_{(e^{+},e^{-})}^{\mathrm{\text{Co}}}>{\mathrm{\Delta }}_{(e^{+},e^{-})}^{\mathrm{\text{Ni}}}$. Furthermore, there is a correlation between the magnetic moment and electronegativity trend of the TM dopant. Specially, the electronegativity trend (${\chi }^{\mathrm{\text{TM}}})$ is well matched with the total spin moment trend, where ${\chi }^{\mathrm{\text{Ni}}}>{\chi }^{\mathrm{\text{Co}}}>{\chi }^{\mathrm{\text{Fe}}}>{\chi }^{\mathrm{\text{Mn}}}$.

In this research, we have employed the Density Functional Theory (DFT) to successfully study the structural, elastic, thermoelectric, and optoelectronic properties of hexagonal halide perovskites CsGeX₃ ($\mathrm{\text{X}}=\mathrm{\text{I}}$, Cl, and Br). We used the Modified Becke–Johnson (MBJ-GGA) potential approximation to profoundly describe the band structure. The compounds of this interesting study are ductile, anisotropic, and mechanically stable. Our study showed that the optical properties are significant, among which are the following: the absorption is higher in the ultraviolet range, and the transmittance reaches a maximum level, which is 80% in the visible and infrared ranges. These substances can be employed in various optoelectronic systems that work in visible and ultraviolet energies. Furthermore, the transport properties are remarkably improved and reached the ZT $\sim 1$. These characteristics proved that they have an interesting potential for thermoelectric uses. We emphasized that this study provided the theoretical foundation of these structures’ elastic, electronic, and optical properties.

In this paper, using density functional theory (DFT), we present a systematic computational investigation on ZrCl₄ in respect of electronic, structural, optical, mechanical properties, which is of great interest in semiconductor physics. Our results show that the metal tetrachloride is a mechanically stable semiconductor with a wide indirect bandgap of $E_g^{\mathrm{\text{HSE}}03}=4.82$eV ($E_g^{\mathrm{\text{GGA}}}=3.56$eV). ZrCl₄ could behave as a brittle material and could be covalent. According to our optical data, a reflectivity of 27.6% could suggest a good material absorption characteristic on the studied material, with a high absorption coefficient of up to $1.61\times 10^5$cm${}^{-1}$. On the partial density of states plot, the hybridization of electron orbitals between Cl 3p⁵ states in the valence band and transition Zr 4d² states in the conduction band is also observed. Our findings advance the fundamental understanding of ZrCl₄ material and provide important insights in electronic/optoelectronic applications.

The ab initio studies of isomers clearly show the delicate change from sp³ carbon to sp² carbon inside two five-membered rings of these structures, as analyzed by both geometry and electron delocalization of adjacent bonds next to both rings. Electronic origin of 2- with the highest energy among isomers is attributed to the relative increase in orbital energies, localized spatial feature due to lone pairs of chlorines, and π* characteristics for corresponding molecule orbitals. The steric effect not only favors fluorine over phenyl in substituting Cl connected with the 2-C, but also predominates configurations of double-substituted isomers. This work suggests that C_s-C₆₀Cl₆ can serve as one practical substituting template for synthesizing C_s-C₆₀F₆.

Very little information is available about the structural properties of III-nitride binary compounds in the rock-salt phase. We report/review a comprehensive theoretical study of structural properties of these compounds in rock-salt, zinc-blende and wurtzite phases. Calculations have been made using full-potential linearized augmented plane wave plus local orbitals (FP-L(APW+lo)) method as embodied in WIEN2k code framed within density functional theory (DFT). In this approach of calculations, local density approximation (LDA) [J. P. Perdew and Y. Wang, Phys. Rev. B45 (1992) 13244] and generalized gradient approximation (GGA) [J. P. Perdew, K. Burke and M. Ernzerhof, Phys. Rev. Lett.72 (1996) 3865] have been used for exchange-correlation energy and corresponding potential. Calculated results for lattice constants, bulk modulus, its pressure derivative and cohesive energy of these compounds are consistent with the experimental results. Following these calculations, besides many new results for the rock-salt and other phases, a comprehensive review of the structural properties emerges. We also list some peculiar features of these compounds.

CrO₂ has a wide band gap for "down" spins and the Fermi level lies in the middle of the band gap. Calculations based on the local-spin density approximation (LSDA) has been performed to investigate the electronic and physical properties of CrO₂ in the rutile structure (P42/mnm). We considered the semicore electrons as valence electrons and found that CrO₂ appears to be half-metallic with a direct band gap of 1.8 eV in spin-down and has metallic behavior in spin-up configurations.

We hereby are reporting the transition pressure at which lithium fluoride (LiF) compound transforms from direct band gap to indirect band gap insulator on the basis of FP-LAPW calculations. The fundamental band gap of LiF compound suffers direct to indirect transition at a pressure of 70 GPa. The study of the pressure effect on the optical properties e.g. dielectric function, reflectivity, refractive index and optical conductivity of LiF in the pressure between 0–100 GPa, shows that this pressure range is very critical for LiF compound as there are significant changes in the optical properties of this compound.

In this paper, we present ab initio calculations within density functional theory (DFT) to investigate structure, electronic and magnetic properties of Ru₂CrZ (Z = Si, Ge and Sn) full-Heusler alloys. We have used the developed full-potential linearized muffin tin orbitals (FP-LMTO) based on the local spin density approximation (LSDA) with the PLane Wave expansion (PLW). In particular, we found that these Ruthenium-based Heusler alloys have the antiferromagnetic (AFM) type II as ground state. Then, we studied and discussed the magnetic properties belonging to our different magnetic structures: AFM type II, AFM type I and ferromagnetic (FM) phase. We also found that Ru₂CrSi and Ru₂CrGe exhibit a semiconducting behavior whereas Ru₂CrSn has a semimetallic-like behavior as it is experimentally found. We made an estimation of Néel temperatures (T_N) in the framework of the mean-field theory and used the energy differences approach to deduce the relevant short-range nearest-neighbor (J₁) and next-nearest-neighbor (J₂) interactions. The calculated T_N are somewhat overestimated to the available experimental ones.

In this paper, we have carried out a theoretical investigation on the structural and optoelectronic properties of NaCl under pressure effect via first principle calculations within the density functional theory. The structural phase transition from NaCl(B1) to CsCl(B2)-type structures is determined. The compound has a very wide bandgap in both phases. Optical properties including the absorption coefficient, optical conductivity and frequency dependent reflectivity are explained to characterize the optical nature of NaCl up to pressure of 134 GPa.

In this paper, we investigate the structural stability of silicane and germanane under biaxial strain by employing the lattice dynamics calculations within the frame of density functional theory. Our results show that silicane and germanane become unstable even under 1% compressive strain, while maintaining stable under tensile strain. Further calculations about the thermodynamical properties of silicane and germanane show that the phonon contribution to Helmholtz free energy, entropy and specific capacity are insensitive to the tensile strain.

In this paper, the structural, electronic and optical properties of V-doped single-walled ZnO nanotube (8, 0) (SWZnONT (8, 0)) were investigated by the first principles. The calculated formation energy shows that V-doped SWZnONT (8, 0) is more stable than pure SWZnONT (8, 0). Our results show that pure SWZnONT (8, 0) has a direct bandgap about 1.443 eV in Γ point. In the V-doped SWZnONT (8, 0), some bands in both spin down and up cross the Fermi level and the calculated total spin magnetic momentum was obtained about 2.345 μ_B. So we expect that the V-doped SWZnONT (8, 0) exhibits magnetic and metallic behavior. These results are in agreement with other theoretical works. The optical properties such as dielectric function, energy loss function, optical conductivity, refractive index and reflectivity are calculated. Redshift, metallic behavior and anisotropic property were observed in the V-doped SWZnONT (8, 0). Our results suggest that the V-doped SWZnONT (8, 0) can be used in magneto-optical devices. The results showed that the reflectivity of pure and V-doped SWZnONT (8, 0) in the wide energy range is low, therefore, pure and V-doped SWZnONT (8, 0) can be used in transparent coating.

Adsorption of molecular oxygen with a triplet ground state on Fe-, Co-, Ni-, Ru-, Rh-, Pd-, OS-, Ir- and Pt-doped graphene is studied using density functional theory (DFT) calculations. The calculations show that O₂ molecule is chemisorbed on the doped graphene sheets with large adsorption energies ranging from -0.653 eV to -1.851 eV and the adsorption process is irreversible. Mulliken atomic charge analysis of the structure shows that charge transfer from doped graphene sheets to O₂ molecule. The amounts of transferred charge are between 0.375e^- to 0.650e^-, indicating a considerable change in the structures conductance. These results imply that the effect of O₂ adsorption on transition metal-doped graphene structures can alter the possibility of using these materials as a toxic-gas (carbon monoxide, hydrogen fluoride, etc.) sensor.

Structural and magnetic properties as well as the electronic structures of ${\mathrm{\text{Ru}}}_2\mathrm{\text{YGe}}(\mathrm{\text{Y}}=\mathrm{\text{Cr}},\mathrm{\text{Mn}})$ Heusler alloys were investigated in the framework of first principle calculation. Using the full-potential linearized augmented plane wave (FP-LAPW) in connection with the generalized gradient approximation (GGA) treatment of exchange-correlation energy, we have performed the structural optimization in the non-magnetic (NM) and three different magnetic configurations: FM, AFM-I and AFM-II. We have found that our two compounds are stable for the AFM-II state, which agree with the available experimental and theoretical results. The exchange constants $J_1$ and $J_2$ as well as the temperature of transition to the paramagnetic state $(T_N)$ were estimated here by the use of the energy difference method and the mean field approximation. The electronic structure of our compounds in their magnetic state was also studied. The GGA + U method has also been used to take into account the strong correlations among the d orbitals of $\mathrm{\text{Ru}},\mathrm{\text{Cr}}$ and $\mathrm{\text{Mn}}$ atoms. This has considerably improved both the electronic and magnetic results which became close to the corresponding experimental data. We have finally studied the thermodynamic properties using the quasi-harmonic Debye model as implemented in the Gibbs Program.

Our calculations were conducted within density functional theory (DFT) and density functional perturbation theory (DFPT) using norm-conserving pseudo-potential and the local density approximation. The elastic constants of ${\mathrm{\text{Zn}}}_{1-x}{\mathrm{\text{Be}}}_x\mathrm{\text{O}}$ were calculated, $C_{11}$, $C_{33}$ and $C_{44}$ increase with the increase of Be content, whereas the $C_{12}$ shows a non-monotonic variation and $C_{13}$ decreases when Be concentration increases. The values of bulk modulus $B$, Young’s modulus $E$ and shear modulus $G$ increase with the increase of Be content. Poisson’s ratio $\sigma$ decreases with increased Be concentration. The ductility decreases with increasing Be concentration and the compressibility for ${\mathrm{\text{Zn}}}_{1-x}{\mathrm{\text{Be}}}_x\mathrm{\text{O}}$ along $c$-axis is smaller than along $a$-axis. Phonon dispersion curves show that ${\mathrm{\text{Zn}}}_{1-x}{\mathrm{\text{Be}}}_x\mathrm{\text{O}}$ is dynamically stable (no soft modes). Quantities such as refractive index, Born effective charge, dielectric constants and optical phonon frequencies were calculated as a function of the Be molar fraction $x$. The agreement between the present results and the known data that are available only for ZnO and BeO is generally satisfactory. Our results for ${\mathrm{\text{Zn}}}_{1-x}{\mathrm{\text{Be}}}_x\mathrm{\text{O}}$$(0<x<1)$ are predictions.

In this paper, some optical properties of pure and transition metal-doped (TM = Co and V) single-walled ZnO nanotubes (8,0) (SWZnONT(8,0)) such as, real and imaginary parts of the dielectric function, optical conductivity, refractive index and optical reflectivity, were investigated. The calculations have been performed within framework of the density functional theory (DFT) using the full potential linearized augmented plane wave (FP-LAPW) and the generalized gradient approximation (GGA). The results show that, optical properties of SWZnONT(8,0) are anisotropic, especially at low energies and this anisotropy at low energies increases with doping of V in SWZnONT(8,0) while the Co-doped SWZnONT(8,0) behaves like pure SWZnONT(8,0). Doping of ZnO nanotubes has a significant impact on the value of the dielectric constant, so that due to the presence of V atom, the dielectric constant is increased up to three times. Study of the imaginary part of the dielectric function and optical conductivity showed that the important energy range for absorption processes and optical transitions is low energy range to 15 eV. The optical transitions have been studied based on band structure and density of states. The results of the optical reflectivity showed that these nanotubes are transparent in a wide energy ranges which provide them for using in transparent coatings. In addition, due to the reported magnetic properties for V- and Co-doped ZnO nanotubes, these nanotubes are suitable for using in spintronics and magneto-optic devices.

This paper studies the mechanical properties of polyethylene (PE)–Single-walled carbon nanotube (SWCNT) complexes by using density functional theory (DFT). At the PBE/SVP level, the Young’s modulus of the complexes is obtained as a function of PE content. It is established that, with increasing number of PE chains attached to the SWCNTs, the Young’s modulus monotonically decreases. The density of states (DOS) results show that no orbital hybridization exists between the PE chains and nanotubes. The results of this work are of importance for the design of composite materials employing SWCNTs.

The structural and elastic properties of neutral and ionized dichlorocarbene (CCl₂) functionalized single-walled carbon nanotubes (SWCNTs) were studied using density functional theory (DFT). The Young’s modulus of ionized pristine SWCNTs is found to decrease in comparison to that of neutral models. The interesting effect of increase in Young’s modulus values of ionized functionalized SWCNTs is observed. We ascribe this feature to the concurrent processes of the bond elongation on ionization and the local deformation on cycloaddition. The strong dependence of the elasticity modulus on the number of addends is also observed. However, the CCl₂-attached SWCNTs in their neutral and ionized forms remain strong enough to be suitable for the reinforcement of composites. In contrast to the elastic properties, the binding energies do not change significantly, irrespective of CCl₂ coverage.