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Raibareli, India

Sharma R.,Feroze Gandhi Institute of Engineering and Technology | Dwivedi S.,Feroze Gandhi College | Sharma Y.,Feroze Gandhi College
International Journal of Hydrogen Energy | Year: 2015

Ternary intermetallic YPd3 is known to exhibit superior hydrogen storage capacity compared to pure palladium. To understand the characteristics of YPd3 on hydrogenation, the ground state electronic and dynamical properties were computed by two computational methods, the full potential linearized plane wave and projector augmented wave methods within the density functional theory. Hydrogen can be inserted in YPd3 at various octahedral sites, giving rise to model structures YPd3H and YPd3H4 which retain the L12 crystal structure. The calculated energy bands confirm the metallic nature of YPd3 and also exhibit greater dispersion of bands with increase in hydrogen content. Large variations in the optical constants such as transmittance is observed (by ∼40% in the violet region) with insertion of hydrogen, YPd3 may have thus have applications as a sensing device for monitoring hydrogen for using hydrogen safely. The electronic component γ obtained from the temperature dependent specific heats, is related to the density of states at the Fermi level which may be co-related to instability of hydrides. The modes at Γ-point in YPd3H and at X and M-points in YPd3H4 give rise to high peaks in the imaginary frequency regime which could drive the dynamical instabilities. From the formation energies and phonon modes it is found that the monohydride YPd3H is more stable, thus occupation of the octahedral sites at 2Y4Pd by hydrogen atoms results in greater dynamic instability in YPd3. © 2014 Hydrogen Energy Publications, LLC.

Root-rot caused by Rhizoctonia solani is a destructive disease of French bean (Phaseolus vulgaris) in the northern plains of India. A randomized block design field experiment was laid out in loam soil containing low organic carbon, nitrogen and medium available phosphorus to evaluate the disease controlling potential of soil inhabiting arbuscular mycorrhizal fungi (AMF) and bacteria. Plants treated with AMF either alone or in combination with Pseudomonas fluorescens, could endure the root-rot incidence under field conditions and produced higher pod yield. Combined inoculation of AMF + P. fluorescens was more effective for controlling the disease as well as increasing the yield. Addition of mustard oil cake to dual inoculation i.e. AMF + P. fluorescens was found highly effective. AMF + p dose chemical phosphorus also improved pod yield and 100-seed weight even in R. solani infected plants. Mixed inoculations along with mustard oil cake were found best treatments for root-rot disease control management. © 2011 Elsevier Masson SAS.

Srivastava P.,Feroze Gandhi College | Singh Mund H.,University of Rajasthan | Sharma Y.,Feroze Gandhi College
Physica B: Condensed Matter | Year: 2011

The electronic structure of crystalline As2S3 and As2Se3 has been calculated in this paper. We present the energy bands, density of states (DOS) and the Compton profiles using the linear combination of atomic orbitals (LCAO) scheme based on the density functional theory (DFT). From the calculated total and partial density of states it is seen that the lone-pair p-states of sulphur/selenium contribute closest to the Fermi energy level. To interpret the theoretical data on the Compton line shape, we have measured the Compton profiles on a 100 mCi 241Am spectrometer. It is seen that the density functional theory within generalised gradient approximation gives a slightly better agreement with the experimental momentum densities. The nature of chemical bonding in arsenic chalcogenides is studied using Mullikens population analysis and the experimentally measured equal-valence-electron-density profiles; As2S3 is found to be more ionic compared to As2Se3. © 2011 Elsevier B.V.

Sharma Y.,Feroze Gandhi College | Srivastava P.,Feroze Gandhi College
Indian Journal of Pure and Applied Physics | Year: 2011

Transparent conducting oxides have important applications as optoelectronic devices. First principles calculations have been performed to study the electronic and optical properties of Sc-, Y- and Ti-doped transparent conducting oxide (TCO) material CdO. The dielectric functions, absorption coefficients and transmittance spectra have been computed to study the effect of doping. The density of states have also been investigated to interpret the calculated optical spectra in terms of inter band transitions. The valence electron charge density is plotted to understand the redistribution of charges on introduction of transition metal ions. The electrical conductivity and Hall coefficient have also been calculated. The calculated band gap for pure CdO which is 0.51 eV increases significantly with doping. The band gaps for Sc-, Y- and Ti- doped CdO are 2.67, 2.83 and 2.53 eV, respectively, which are in good agreement with experimental measurements.

Sharma R.,Mewar University | Sharma R.,Feroze Gandhi College | Sharma Y.,Feroze Gandhi College
International Journal of Hydrogen Energy | Year: 2015

Considerable attention has recently been given to bimetallic systems such as Cu-Pd alloys as hydrogen storage material. These alloys are attractive alternatives to pure Pd membranes because of their sulphur tolerance and high permeability to hydrogen. The density functional theory based full potential linearized augmented plane wave and projector augmented wave methods have been implemented to understand the phenomenon of hydrogen diffusion in Cu-Pd alloys. The AuCu3 structure of CuPd3 and Cu3Pd allows intercalation of hydrogen atoms in its octahedral sites. The lattice parameters and volume of the unit cell expand on hydrogenation, without phase change. We have studied the formation and stability of hydrides of the ternary alloys. The heats of formation support the hydrogenation of CuPd3 alloy whereas the endothermic reactions indicate that hydrogen will be absorbed in the Cu3Pd alloy at the expense of energy. The phonon dispersion relations of the hydrides of CuPd3 exhibits instability due to the Pd-H bonds which leads to distortion of Pd-octahedra in the unit cell. Softening of acoustic modes is not observed in the Cu3Pd alloy; instead the optical modes due to H-H bonds have very high vibrational frequencies. The permeance of H atoms in the alloy can be quantified from the extent of hybridization between H s-states, Cu and Pd d-states. From the density of states, the movement of the H s-band and centre of d-bands towards the Fermi energy level EF was observed. Both the factors indicated that the monohydride of CuPd3 was most stable. The temperature dependent Hall and Seebeck coefficients reflect the modifications in the electronic structure due to formation of hydrides. At ambient temperatures, the free charges carriers (electrons) are found to increase in the monohydride of Cu3Pd, whereas it decreases in the monohydride of CuPd3. The electronic component of specific heats γ obtained from low temperature specific heats is found to decrease in the hydrides of both the alloys, which implies an increase in the lattice contribution through the electron-phonon coupling. From the optical properties, it is possible to monitor the hydrogen uptake in the alloys by studying the variations in reflectance, absorption coefficients in the visible regions. The electronic and dynamical studies suggest that the alloy with excess Pd has potential applications as hydrogen storage materials. The monohydride of CuPd3 appears to be appropriately stable for applications such as electrode material in rechargeable batteries. © 2015 Hydrogen Energy Publications, LLC.

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