Comparative Thermoluminescence Study of Rare Earth (Eu3+,Dy3+) and Transition Metal Mn2+ with Aluminate Host

The synthesis and characterization of Eu3+ Dy3+ and Mn2+ doped CaYAl3O7 phosphor with fixed 1 mol% concentrations  are reported herewith  to study the kinetic and  Thermoluminescence (TL) properties. The TL glow curve exhibit a  peak centered around ~350°C ,for all three dopants. The  Mn2+ ion  is exhibits intensive peak to other dopants. . Determine the activation energy and kinetic parameters of these material  using Chen’s formula. These results are supported by corresponding X-ray diffraction measurements which exhibit crystalline nature. These comparative analysis   suggest the possibility of utilizing this material in futuristic dosimeter application as well as in solid state lighting devices. Keywords: Thermoluminescence ,Phosphor, Dosimete

First Principles Study on Structural and Electronic Properties of REAg (RE= Y, La, Pr and Er) Intermetallics

We The structural, electronic and mechanical properties of binary B2 – type CsCl structured intermetallic compounds of Ag (ReAg, Re= Y, La, Pr and Er) have been studies systematically by means of first principles density functional theory within generalized gradient approximation. Ground state properties such as lattice constant (a0), bulk modulus (B) and its pressure derivative (B?) are obtained. The present results are in good agreement with the experimental and other theoretical calculation available. Amongst all the Intermetallics is found ErAg to be most ductile due to the presence of strong metallic bonding. Keywords: Intermetallic compounds; Density Functional Theory; Ductility; Electronic Structure

Ab-initio Study of Structural, Electronic and Elastic Properties of ErCu

First principles density functional calculations were performed to study the structural, electronic, elastic and mechanical properties of erbium copper intermetallic compound (ErCu). The calculations are carried out within the generalized gradient approximation (GGA) for the exchange and correlation potential. The total energy as a function of volume is obtained by performing spin-polarized calculation. Magnetically the ErCu compound is stable in ferromagnetic (FM) state and its crystal structure is CsCl-type. Ground state properties such as lattice constant (a0), bulk modulus (B), its pressure derivative (B?) and magnetic moment (?B) are calculated. The density of states at the Fermi level, N(EF) and specific heat coefficient are also estimated in majority and minority spin channels. The electronic properties such as band structure and density of states (DOS) reveal that no band gap lead to metallic character of ErCu. The elastic constants (C11, C12 and C44) and mechanical properties such as Poisson’s ratio (? ), Young’s modulus (E), shear modulus (GH), anisotropic factor (A) are also calculated .  Ductility for these compounds is further analyzed by calculating  the ratio of (B/GH )  and Cauchy pressure (C12 - C44). Keywords: Density functional theory, Band structure, Density of states, Lattice constant, Bulk Modulus, Specific heat

A First Principle Study of Pressure Induced Structural and Electronic Properties in Neptunium Bismuthide

We have examined the pressure induced structural and electronic   properties of neptunium monobismuthides. The total energy as a function of volume is obtained by means of self-consistent tight binding linear muffin-tin-orbital (TB-LMTO) method within the local density approximation (LDA). It is found that NpBi is stable in NaCl – type structure under ambient pressure. We predict a structural phase transition from NaCl-type (B1-phase) sructure to CsCl-type (B2-phase) structure for NpBi in the pressure range of 11 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 NpBi exhibit metallic behaviour. The calculated equilibrium lattice parameters and bulk modulus are in general good agreement with available experimental data. Keywords: Structural phase transition; Electronic band structure; Metallic

Phonon anomalies in HfN

The phonon dispersion curve are determined by model (BSM) for the crystals transition metal mono-nitride (HfN) and compared with the experimental phonons, which forms perhaps the best test for this purpose. The eight numbers of parameters of the model are determined by using the some set of input data. The results and degrees of agreement obtained in each case show clearly the superiority of the “charge-transfer mechanism” for representing the deformations of electron shells used in the BSM. The phonon dispersion curves and phonon density of states in HfN have been measured in high-symmetry directions Δ, Σ and Λ by breathing shell model (BSM). Anomalies in the dispersion of the acoustic branches and optical branches have been detected which are well described by experimental results

Effect of doping on dynamical properties of diluted magnetic semiconductors

440-444<span style="font-size:14.0pt;line-height: 115%;font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" color:black;mso-ansi-language:en-in;mso-fareast-language:en-in;mso-bidi-language:="" hi"="" lang="EN-IN">The effect of doping of Mn2+ impurity on vibrational properties of IV -VI compounds using three body force rigid ion model has been investigated. Pb-Mn-Te and Sn-Mn-Te systemic with different Mn+ ion concentrations have been considered. Our results show faster softening of TA mode at L point in the Brillouin zone due to Mn2+ substitution.</span

Structural and elastic properties of rare-earth nitrides at high pressure

114-118The structural and elastic properties of rare earth nitrides (REN) [RE=Tb, Ce] under high pressure have been investigated by using two body inter ionic potential theory with modified ionic charge (Zme) to include Coulomb screening effect. The present theoretical approach has predicted pressure-volume relationship curves which show that TbN and CeN exhibit a NaCl type structure at an ambient pressure and undergo a structural phase transition from NaCl into CsCl phase at 136 GPa and 88 GPa, respectively. The Second order elastic constants (SOECs), Third elastic constants (TOECs) and second order pressure derivatives for these compounds have also been reported. The variation of elastic constants (C₁₁, C₄₄) with pressure is also presented

Lattice dynamics of thorium pnictides and chalcogenides

109-114The phonon spectra of thorium pnictides and chalcogenides (ThX) have been analysed using rigid ion and breathing shell models, in view of their structural properties at high pressure. The significance of these two approaches in predicting the dynamical properties of ThX compounds has been discussed and the role of f-electron has been examined. The dominant ionic nature of bonding has been predicted for ThX compound from the large LO-TO phonon splitting at zone centre. The low temperature specific heat for these compounds has been reported

Electronic properties of MoSi₂

634-637The electronic structure and ground state properties of MoSi2 have been studied using first principles density functional theory (DFT). The full potential linearized augmented plane wave (FP-LAPW) method within the generalized gradient approximation (GGA) and local spin density approximation (LSDA) for exchange correlation have been used for calculation of total energy. The ground state properties such as equilibrium lattice constants (<i style="mso-bidi-font-style: normal">a0, c0), bulk modulus (B), its pressure derivative (B′) are computed. Apart from the density of states N(EF), specific heat coefficient (γ) are also estimated and compared with the experimental data. The density of states at the Fermi level N(EF) is 0.25 states/eV for MoSi2. The band structure and density of states around the Fermi level suggest that this compound is semi-metal in nature. The calculated parameters are found to be in overall good agreement with the experimental data

High pressure study of structural and elastic properties of barium chalcogenides

722-726The structural and elastic properties of barium chalcogenides (BaX; X = S, Se, Te) under high pressure have been investigated by using a two body inter-ionic potential approach with modified ionic charge (Zme). The equation of states in NaCl type to CsCl type structural phases for BaX has been depicted and found that the volume collapses at the phase transition pressures. The phase transition pressures 7.2 GPa, 6.1 GPa, 5.0 GPa respectively for BaS, BaSe, and BaTe obtained by us, are in close agreement with experimental data (6.5 GPa, 6.0±0.2 GPa, 4.8±0.3 GPa). The bulk modulus, pressure derivatives, second order elastic constants (SOEC) and third order elastic constants (TOEC) at high pressure have been calculated, which show predominantly ionic nature of these compounds. The variation of second order elastic constants (C₁₁, C₄₄) with pressure has been presented