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Structural, electronic and optical properties of InAs phases: by GGA-PBG and GGA-EV approximations
摘要： Structural, electronic and optical properties of InAs are investigated in the zinc-blende (ZB), rock-salt (RS) and wurtzite (WZ) phases using the full potential linearised augmented plane wave method in the framework of density functional theory (DFT). The electronic band gap of the ZB and WZ phases are improved and in good agreement with experiments by GGA-EV approximation. This compound has a direct band gap in the ZB and WZ phases in Γ point at the centre Brillouin zone and in the RS phase the conduction band crosses towards the valence band and has metallic behaviour. Also, the optical parameters such as the real and imaginary parts of epsilon, energy loss, and the refraction and reflection indices of all the phases are calculated and compared. The calculated optical properties of InAs have promising applications such as the design of optoelectronic and photonic devices.
关键词： density functional theory,optical property,GGA-EV,electronic property,InAs
更新于2025-09-23 15:22:29
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Elastic and optoelectronic properties of CaTa2O6 compounds: Cubic and orthorhombic phases
摘要： Using first principles density functional theory (DFT) simulations, the structural, electronic, optical and elastic properties of CaTa2O6 oxide for cubic and orthorhombic phases are studied by highly accurate (FP-LAPW) method within the GGA + U approximation. The calculated lattice parameters are consistent with available experimental data. The electronic band structure calculations have shown that the band gaps in CaTa2O6 are equal to 3.08 eV and 4.40 eV for the cubic and orthorhombic structures, respectively. For both the phases the main optical properties, e.g., absorption coefficient, dielectric constant, energy loss function, and reflectivity, refractive index, and extinction coefficient are calculated and discussed in detail in the spectral range 0-14 eV. Cubic and orthorhombic phases exhibit significantly different optical characteristics. The electronic bonding characters of CaTa2O6 with different symmetries are explored via charge density distribution mapping. Strong covalent bonding character dominates in both the phases of CaTa2O6. Elastic properties of CaTa2O6 for cubic and orthorhombic phases are also investigated. The stress strain method is used for the determination of elastic constants in both the phases. The bulk modulus, shear modulus, Young’s modulus, along with the important elastic anisotropy factors and Poisson’s ratio are studied in detail.
关键词： First principles density functional theory,GGA+U approximation,FP-LAPW method,Optical constants,Electronic band structure,electro technical materials
更新于2025-09-23 15:22:29
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density functional
摘要： It was recently reported in experiments that at temperatures below 2500 K liquid nitrogen (N) remains molecular up to 120 GPa [Phys. Rev. Lett. 119, 235701 (2017)], which contradicts a liquid-liquid transition at 88 GPa and 2000 K predicted by PBE-GGA density functional. To clarify this, we perform extensive ?rst principles molecular dynamics using SCAN meta-GGA density functional, which captures the intermediate-range part of the van der Waals interaction better than PBE-GGA. It is found that SCAN gives more accurate bond energy and length of an isolated N2 molecule than PBE. SCAN, as well as PBE, is capable of reproducing the ?rst-order molecular-to-polymeric phase transition, but in contrast to PBE, it predicts a wider stability range for ?uid N2. The boundary of this range is 15 GPa higher than the one predicted with PBE, which is in closer agreement with experiments. In addition, SCAN predicts a higher amount of threefold coordinated atoms in the polymeric phase than PBE, which is expected from experiments in amorphous N. These improvements indicate that SCAN is more accurate than PBE in predicting the phase transition from molecular to polymeric ?uid N.
关键词： phase transition,density functional,molecular dynamics,SCAN meta-GGA,liquid nitrogen
更新于2025-09-23 15:21:01
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Ab-initio study on electronic and magnetic properties of (Ga,Co) co-doped ZnO
摘要： Using first-principles calculations based on density functional theory within GGA formalism, we have studied the electronic structure and magnetic properties of (Ga,Co) co-doped ZnO system. The effect of impurity distances on ferromagnetic and antiferromagnetic ground state in Co0.056Zn0.944O has been studied. For the closest Co-Co distance, a ferromagnetic ground state with total magnetic moment of ~3.00μμ’ per Co atom has been found. The electronic structure also displays a nearly halfmetallic order. Conversely, for the farthest Co-Co distance an antiferromagnetic ground state was found for Co0.056Zn0.944O. When Zn2+ ions are replaced by Ga ions in Co0.056Zn0.944O, the new (Ga,Co) co-doped ZnO system is more energetically stable. It has also been found that Ga-doping reduces the Co0.056Zn0.944O band gap due to the sp-d exchange interactions, which is in good agreement with the experimental data. Moreover, the Ga-doping changes the nearly halmetallic order of Co0.056Zn0.944O to metallic. Results also show that Ga0.029Co0.056Zn0.915O is still ferromagnetic with a total magnetic moment of ~3.00μμ’ per Co atom. It was also found that the ferromagnetic ground state in (Ga,Co) co-doped ZnO vanishes as Ga concentration increases.
关键词： GGA formalism,(Ga,ab-initio,density functional theory,electronic structure,Co) co-doped ZnO,magnetic properties
更新于2025-09-04 15:30:14
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[IEEE 2018 15th International Multi-Conference on Systems, Signals & Devices (SSD) - Yassmine Hammamet, Tunisia (2018.3.19-2018.3.22)] 2018 15th International Multi-Conference on Systems, Signals & Devices (SSD) - The New Candidate Materials for Infrared Optical Devices
摘要： In this study, We propose the cubic AlxB1-xBi ternary alloy as a promising infrared material. We used the full potential-linearized augmented plane wave (FP-LAPW) method within the Density Functional Theory (DFT) to predict the structural and electronic properties of the AlxB1-xBi ternary alloys. The structural properties such as the equilibrium lattice parameter, bulk modulus, and its pressure derivative are investigated with the effect of the concentration variation of Al atom, x (x=0, 0.25, 0.50, 0.75 and 1). We found that the equilibrium lattice parameter of AlxB1-xBi ternary alloys increases when increasing the doping concentration of the Al atom, while its bulk modulus decreases. The energy band gap of the AlxB1-xBi ternary alloys decreases with the increase in the Al doping concentration. The AlxB1-xBi alloys for 0.50 and 0.75 present a semi-metallic character the other concentrations and are compositions. Our results show the direct nature of the energy band gap of the ternary AlxB1-xBi alloy for all composition of Al substitution. To our knowledge, this is the first theoretical study of this ternary alloy that needs eventual experimental data for confirmations.
关键词： Optical properties,TB-MBJ,FP-LAPW,Electronic structure,GGA,DFT,Infrared Radiation,III-III-V ternary Alloy
更新于2025-09-04 15:30:14