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The interaction of H, H2, and MgH2 with graphene is investigated using the density functional theory to explore the possibility of exploiting graphene or functionalized graphene as a hydrogen storage medium. The H atom is positioned at various distances from the graphene surface and the energetics are computed in detail. The extent of interaction of the s electron of H with graphene's pz electrons is well brought out. Similar investigations are carried out for H2, MgH2. In the case of H atom, a HC covalent bond is formed. This process turns out to be a prerequisite for proton transfer through graphene. Interactions of H2 and MgH2 with graphene are different from that of H. It leads to the conclusion that functionalized graphene will better substrate/candidate for applications like hydrogen storage. [ABSTRACT FROM AUTHOR]

Using density functional theory, we have analyzed the ways and means of improving the minority carrier lifetime (MCL) by calculating the band structure dependent quantities contributing to the MCL. We have computationally modeled silicon doped with different elements like B, C, N, O, P, Ti, Fe, Ga, Ge, As, In, Sn, Sb, and Pt and looked at the effect of doping on MCL. In co-doping, the systems Si-B-Ga, Si-B-Ge, Si-B-2Ge, Si-B-Pt, Si-Ga-Ge, Si-Ga-2Ge, and Si-Ga-Pt are investigated. From our calculation, it is found that by doping and co-doping of Si with suitable elements having “s” and “p” electrons, there is a decrease in the recombination activity. The predicted effective minority carrier lifetime indicates the possibility of significant improvements. Based on the above studies, it is now maybe possible, with suitable choice of dopant and co-dopant material, to arrive at part of a standard production process for solar grade Si material. [ABSTRACT FROM AUTHOR]

The electronic structure and optical properties of AgIn1−xGaxY2 (Y = Se, Te) are investigated using first-principles calculations based on density functional theory. Both the local density approximation (LDA) and generalized gradient approximation (GGA) are employed in the calculation. The crystal structure of ternary semiconductors is the tetragonal chalcopyrite structure with space group I 4 ¯ 2d . The lattice parameters a(Å) and c(Å) are found to vary with the change in Ga composition. The energy gap across the Fermi level in the density of states plots shows that these materials are semiconductors. To compute accurate energy gap values, the LDA + U method is adopted. The calculated elastic constants indicate that these compounds are mechanically stable at normal pressure. The semiconducting nature of these materials may prove their applications in solar cells and photovoltaic absorbers. The optical parameters such as dielectric function, electron energy loss function, refractive index and reflectivity are computed. [ABSTRACT FROM AUTHOR]

The structural, electronic and mechanical properties of AgIn1−XGaXS2 (X = 0, 0.25, 0.50, 0.75, 1) chalcogenides are investigated. The crystal structure of ternary semiconductors is the chalcopyrite structure with space group I 4 ¯ 2 d . In this work, first principles calculations are carried out based on density functional theory within the local density approximation to analyze the structural, electronic and mechanical properties of chalcogenides. The calculated lattice constant values are in good agreement with the available data. The lattice constants and the energy gap value increase with the increase in concentration of Gallium (Ga) in AgIn1−XGaXS2. The electronic structure reveals that these materials are semiconductors. The calculated elastic constants indicate that these chalcogenide materials are mechanically stable at normal pressure. The semiconducting nature of these materials may prove their applications in solar cells and photovoltaic absorbers. [ABSTRACT FROM AUTHOR]

The structural property, electronic structure and optical properties of lead-based halide perovskites CsPbF3-yIy (y = 0, 1, 2) are investigated. The computed electronic structure profile of CsPbF3-yIy (y = 0, 1, 2) reveals that these materials exhibit semiconducting behavior at normal pressure. The energy gap of CsPbF3 is tuned by substituting iodine atoms for fluorine atoms. The optical parameters, such as dielectric function, electron energy loss function, refractive index and reflectivity, are computed. The optical properties of these lead-based halide perovskites against the incident photon energy radiation indicate that these materials can be effective candidates for the solar cell applications. [ABSTRACT FROM AUTHOR]