Papers by Keyword: Electronic Band Structure

Abstract: We explore the structural and electronic properties of a single layer arsenene using the state of art, first principle approach from density functional theory (DFT). All the calculation was conducted using an open source DFT code, adopted the planewaves (PWs) method by Quantum Espresso (QE). The calculation utilized an exchange correlation potential of electron parametrized by Perdew-Burke-Ernzerhof (PBE) under generalized gradient approximation (GGA) functional scheme. Meanwhile, the pseudopotential assigned for the core electron is the projector typed augmented-wave with the core potential correction, generated using "atomic" code. All those parameters resulted an optimized structure of the honeycomb arsenene with lattice constant of 4.4971 Ǻ. The arsenene layer occupy a bond length value of 2.5964 Ǻ as measured between its neighbouring bonded atoms. From an optimized structure, we explore its electronic bandstructure plotted from 3 highly symmetries point for 2-dimensional (2D) material known as ‘’, ‘’ and ‘’ with 3 electron pathways. The total number of bands considered in bandstruture plotting is 10, where 5 bands will consider as valance bands while another 5 is conduction bands. The bandstructure shows that a single layer flat arsenene exhibits the characteristics of a conductor due to the overlapping of band near to Fermi level. Dirac cone were also noticed near to the Fermi energy level of the bandstructure. Lastly, we study the total electron density for the whole structure to reveal its bonding characteristics. The contour plot of electron densities between two bounded atoms displayed a pure covalent bond characteristic. The findings of this work is expected to contribute to the key of the electronic devices development, optoelectronics, and sensor devices based on 2D material technology.Keywords: flat layer arsenene, density of state, electron density, electronic band structure

Abstract: The tight binding linear muffin-tin-orbital (TB-LMTO) method within the local density approximation (LDA) is used to study the electronic structure and high pressure behaviour of thulium compounds TmX (X= P, As, S, and Se). We also predict a structural phase transition from NaCl to CsCl-type structure. The transition pressures were found to be 40.0, 31.0, 58.0 and 49.0 GPa, for TmP, TmAs, TmS and TmSe respectively. Apart from this, the lattice parameter (a₀), bulk modulus (B₀), band structure and density of states are calculated. From energy band diagram, it is observed that these compounds exhibit weak metallic character. The calculated values of lattice parameters and bulk modulus are of reasonable agreement with available data.

Abstract: The density functional theory within generalized gradient approximation (GGA) has been used to calculate lattice parameter, total energy, phase transition pressure and electronic properties of neptunium sulphide (NpS). From our calculations we observe that NpS is stable in NaCl – type structure under ambient pressure. For this compound, the phase transition pressure was found to be 29.5 GPa. The nature of metallic behaviour is remarked from energy band diagram in NpS. All properties obtained for this compound are in good agreement with available results.

Abstract: The electronic, elastic and mechanical properties of neptunium bismuthide have been studied systematically using first principles density functional theory within generalized gradient approximation. Ground state properties such as lattice constant (a₀), bulk modulus (B), its pressure derivative (B′) and elastic constants are calculated. The present results are in good agreement with the experimental and other available theoretical results. Poisson’s ratio (σ), Young’s moduli (E), shear moduli (G_H) and the ratio of elastic anisotropy factor (A) are also estimated.

Abstract: The electronic structure and high pressure structural phase transition of SmTe and SmPo have been studied by using tight binding linear muffin-tin-orbital (TB-LMTO) method within the local density approximation (LDA). The total energy as a function of volume is obtained and it is found that these compounds are stable in NaCl-type (B₁-phase) structure and transform to CsCl-type (B₂-type) structure. The transition pressure of SmTe and SmPo are found to be 6.6 GPa and 8.6 GPa respectively. We have also calculated lattice parameter (a₀), bulk modulus (B₀), band structure (BS) and density of states (DOS). From energy band diagram, we observed that these compounds exhibit weakly metallic behaviour. The calculated values of lattice parameter and bulk modulus agree well with the available data.

Abstract: The ground state and electronic properties of americium pnictides (AmY, Y=N, P) has been calculated with the help of tight binding linear muffin-in-orbital (TB-LMTO) method within the local density approximation (LDA). From present study it is found that AmN and AmP are stable in NaCl – type structure under ambient pressure. The structural stability of AmN and AmP changes under the application of pressure. We predict a structural phase transition from NaCl-type to CsCl-type structure for these Am-pnictides in the pressure range of 36.0 – 47.0 GPa (AmN-AmP). Optimized lattice parameters, transition pressures and bulk modulus were obtained for the first time and analyzed in comparison with the available theoretical and experimental data.

Abstract: Tetratenite phase of L1₀ (CuAu) FeNi is identified as a hard ferromagnet in spite of that common FeNi alloys are classified as a soft magnet. Due to its strong magnetic anisotropy and large coercivity, tetrataenite phase of L1₀ FeNi is under investigation as a rare earth free advanced permanent magnet. Our computed equilibrium lattice constant and c/a ratio for tetratenite phase of L1₀ (CuAu) FeNi are in 10 % deviation with the other available results. The vibrational and electronic properties of L1₀ FeNi at finite temperatures/pressures are studied using the first-principles plane wave self-consistent method under the framework of density functional theory. Conclusions based on the phonon dispersion curves, phonon density of states and electronic band structure along with total and projected density of states at finite temperatures/pressures are outlined.

Abstract: We have investigated the pressure induced structural and electronic properties of plutonium pnictides (PuY, Y= P, As, Sb). The total energy as a function of volume is obtained by means of self-consistent tight binding linear muffin-in-orbital (TB-LMTO) method within the local spin density approximation (LSDA). From present study with the help of total energy calculations (spin polarized) it is found that PuP, PuAs and PuSb are stable in NaCl – type structure under ambient pressure. The structural stability of PuP, PuAs and PuSb changes under the application of pressure. We predict a structural phase transition from NaCl-type (B₁-phase) to CsCl-type (B₂-phase) structure for these Pu-pnictides in the pressure range of 20.8 – 42.0 GPa. We also calculate the lattice parameter, bulk modulus, band structure and density of states. From energy band diagram it is observed that all the three compounds exhibit metallic behaviour. The calculated equilibrium lattice parameters and bulk modulus are in good agreement with available experimental data.

Abstract: We report ab initio calculations of pressure induced structural phase transition and electronic properties of thulium nitride (TmN). The total energy as a function of volume is obtained by using the self-consistent tight binding linear muffin-tin-orbital (TB-LMTO) method within the local density approximation (LDA). It is found that TmN is stable in NaCl – type structure under ambient pressure. We predict a structural phase transition from NaCl-type (B₁-phase) structure to CsCl-type (B₂-phase) structure of this compound at a high pressure of 68 GPa. We also calculate the lattice parameter (a₀), bulk modulus (B₀), band structure and density of states. From energy band diagram it is observed that TmN exhibit metallic behaviour. The calculated values of equilibrium lattice parameter and bulk modulus are in general good agreement with available experimental data.

Abstract: The tight-binding linear muffin-tin orbital (TB-LMTO) with in the local density approximation is used to calculate total energy, lattice parameters, bulk modulus, density of states and energy band structures of americium monochalcogenides at ambient as well as high pressure. It is found that AmX (X=S, Se, Te) compounds are stable in NaCl – type structure under ambient pressure. We predict a structural phase transition from NaCl-type (B₁-phase) structure to CsCl-type (B₂-phase) structure for these compounds in the pressure range of 26.0 – 15.0 GPa (AmS to AmTe). From energy band diagram it is observed that AmX compounds exhibit metallic behaviour. The calculated ground state properties such as lattice parameters and bulk modulus are in general good agreement with available experimental and theoretical data.