Papers by Keyword: GGA

Abstract: The crystal structure, electronic and optical properties of organic molecular crystal Trans-4-(trifluoromethyl) cinnamic acid (4-TFMCA, C₁₀H₇F₃O₂) were studied using the density functional theory (DFT). Since 4-TFMCA undergoes solid-state photodimerization under an external light source (UV), the optical properties were a subject of interest. In the calculations, experimental lattice parameters were obtained from previous studies and used as an initial geometry. Structural optimization was achieved using the vdW-DF2 functional with norm-conserving pseudopotentials (NCPP). To optimize the crystal structure, the Birch-Murnaghan equation of state (EOS) was used, and the total volume showed a decrease of 2%. The electronic band structure of the 4-TFMCA crystal was first calculated. The electronic and optical band gaps were predicted, and an artificial acceptor level, attributed to the unsaturated carbon and hydrogen atoms in the molecule, was observed. Additionally, optical properties such as the dielectric function, reflectivity, loss function, refractive index, and absorption coefficient were computed.

Abstract: We have investigated the magnetic properties of semiconducting molybdenum disulfide (MoS₂) monolayer (ML) using the plane wave self-consistent field (PWscf) method within the framework of density functional theory (DFT). The pristine semiconducting bulk MoS₂ is nonmagnetic (NM), due to the spin pairing of two electrons. We have indicated that the carrier-mediated ferromagnetism is available on the MoS₂ ML as both the hole and electron carriers. The ordinary neutral S (V_S⁰) vacancy creates the localized vacancy defect level and this level does not create the ferromagnetic (FM) state due to the spin pairing of two electrons by three Mo dangling bonds. While we have shown that the FM state is possible to create the FM state, due to the additional hole and electron carriers on the valency band and localized vacancy defect level by positively and negatively charged S (V_S¹⁺ and V_S^1- ) and positively charged Mo (V_Mo¹⁺) vacancies.

Abstract: Spinel Li₄Ti₅O₁₂ (LTO) is one of the most promising candidate anode material for Li-ion battery (LIB) known, as zero strain material, it has poor intrinsic electronic properties. In order to enhance it, we have investigated effect of doping on electronic conductivity of spinel LTO phase structure. We consider the carrier and transition metal doping effect on structure and electronic structure of spinel LTO. It is shown that the doping can improve the electronic conduction of spinel LTO. Our calculations were based on the projector augmented wave (PAW) method with the generalized gradient approximation (GGA+U+J₀) including the Hubbard U parameter for exchange correlation functional within the framework of density functional theory (DFT).

Abstract: First principle calculations are carried out to investigate the ground state electronic and magnetic properties of G-type antiferromagnetic (AFM) LaCrO₃ compound in orthorhombic phase. The orthorhombic LaCrO₃, a distorted GdFeO₃ – type perovskite exhibits AFM transition at ~290 K. Additionally; this system shows weak ferromagnetism at room temperature, in conjugation with its semiconducting properties. In this paper, we will discuss the onset of weak ferromagnetism and electronic properties of LaCrO₃, implementing generalized gradient approximation for exchange correlation potential. We present results for electronic structure and density of states, including the effect of onsite Coulomb interaction and non-collinear arrangement of Cr³⁺ magnetic ions in G-type AFM geometry.