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Now showing items 1 - 5 of 5

  • First Principles Calculations on Crystal and Electronic Structure of Co2P4O12

    Rerksompus, Pathompong   Sarasamak, Kanoknan   Boonchom, Banjong   Thanomngam, Pitiporn  

    Crystal and electronic structure of violet-pink Co2P4O12 have been investigated using first principles calculations based on density functional theory. Its theoretical X-ray diffraction and X-ray absorption fine structure spectra were calculated and compared with their experimental spectra to verify its monophasic. The calculated spectra are in good agreement with the experimental data giving parameters of a = 11.993 angstrom, b = 8.328 angstrom, c = 10.150 angstrom and beta = 118.51 degrees. Our calculations on band structure and density of states of Co2P4O12 showed that its major electronic transition is associated with internal Co-3d. The calculations indicated that Co2P4O12 is a half metal ferromagnetic material which disagreed with the experimental knowledge.
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  • First-Principles Investigation on Structural and Electronic Properties of Ferromagnetic Fe2P4O12

    Rerksompus, Pathompong   Sarasamak, Kanoknan   Boonchom, Banjong   Thanomngam, Pitiporn  

    Structural and electronic properties of Fe2P4O12 have been investigated using first-principles calculation technique. The results indicated that the Fe2P4O12 structure is monoclinic of C-2/c with lattice parameters of a =3D 12.228 angstrom, b =3D 8.530 angstrom, c =3D 9.835 angstrom and =3D 118.67 degrees. Two nonequivalent octahedral FeO6 from the calculation have an average Fe-O distance of 2.143 angstrom. Both FeO6 are dominated by covalent interactions assigned to Fe-3d and O-2p at the valent electronic states. The DOS calculation gives well explanation on its half-metallic ferromagnetic property. These results are in very good agreement with the previous experimental reports.
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  • Improvement of energy gap prediction for hybrid perovskite materials by first-principle calculation

    Amnuyswat, Kittiphong   Thanomngam, Pitiporn  

    The breakthrough discovery of pollution free renewable energy has been awarded to conversion of solar energy into electrical energy using planar heterojunction solar cell. A layer of hybrid perovskite light harvesting materials between transport layer and electrode is essential for high power conversion efficiency (PCE). In this work, first-principle calculation based on non-local van der Waals-corrected Density Functional Theory (vdW-DFT) is used to examine atomic structures of the most popular hybrid perovskite materials used in solar cell absorption layer. The optical band gaps achieved from electronic band structures were consistently studied using semi-local exchange-correlation functional (GGA-PBE) and post-DFT approximation (GW approximation). In order to improve band gap accuracy, we tried to compensate relativistic effect in metal ion using spin-orbit coupling (SOC). Our results showed that the energy gap predictions using first-principles GW calculations incorporate with SOC scheme are in good agreement with available experimental reports. Therefore, this calculation scheme is suggested for high accuracy organic-inorganic solar cell design.
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  • Roles of spin-orbit coupling in tetragonal hybrid halide perovskite for photovoltaics light-absorber

    Amnuyswat, Kittiphong   Thanomngam, Pitiporn  

    Hybrid halide perovskite has been gain appropriate attraction because of their relatively high efficiency in most recently solid-state solar cell development. In this work, A first-principle calculation based on non-local van der Waals-corrected Density Functional Theory (vdW-DFT) is performed to investigate high accuracy atomic structures of a tetragonal structure methyl ammonium (CH3NH3) metal (Pb, Sn) halide (Br-3, Cl-3, I-3). The calculated electronic structures were systematically studied using semi-local exchange-correlation functional (GGA-PBE), non-local functional (hybrid HSE06) and post-DFT approximation (GW). A relativistic effect in metal ion was taken into account by incorporating spin-orbit coupling (SOC) effect to obtain more accurate band gap properties of these materials. Our results shown that SOC corrected the electronic structures about 0.92 eV and 0.19 eV in case of lead ion and tin ion, respectively. The combination between GW approximation and spin-orbit coupling show a good agreement between DFT calculations and experimental studies. This computational scheme is necessary for high accuracy organic-inorganic solar cell design. (C) 2018 Elsevier Ltd. All rights reserved.
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  • Effect of exchange-correlation and GW approximations on electrical property of cubic,tetragonal and orthorhombic CH3NH3PbI3

    Amnuyswat, Kittiphong   Thanomngam, Pitiporn  

    A first-principle calculations based on van der Waals-corrected Density Functional Theory (vdW-DFT) is performed to investigate atomic structure of methyl ammonium lead iodine (CH3NH3PbI3) which is a key material for high efficiency solid-state solar cell. A temperature dependent symmetry was previously reported which also included in this study. DFT calculation of electronic and optical properties are systematically studied with semi-local, non-local exchange-correlation and post-DFT approximation including PBE, HSE06 hybrid functional and GW. Relativistic effect in lead ion was taken into account by incorporating spin-orbit coupling (SOC) effect to obtain more accurate band gap of this material. With GW-SOC functional, our results of band gap calculations showed good agreement between DFT calculations and experimental studies which confirmed that this computational scheme is suitable for high accuracy material design, e.g. for solar cell applications.
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