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(searched for: doi:10.33945/sami/ecc.2020.5.2)
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Debashis Howlader, Sayed Hossain, Unesco Chakma, , Mohammad Jahidul Islam, Tawhidul Islam, Tomal Hossain, Jahedul Islam
Published: 18 September 2021
Molecular Simulation, Volume 47, pp 1411-1422; https://doi.org/10.1080/08927022.2021.1977295

Abstract:
As Gallium oxides have been using in optoelectronic devices due to its high potentiality and efficiency, therefore, the Gallium–Copper oxide crystal has been computationally designed and screened for its electronic structure, thermo-electronic and optical properties using density functional theory (DFT). To kick off, GGA) with PBE has been implemented for the crucial screening of its structural geometry and the optimisation for both GaCuO2 and GaCu0.94Fe0.06O2. Afterwards, the electronic structure, thermo-electronic and optical properties were analysed from optimised structures. In addition, for the comparison study of obtained data of the GGA with PBE functional with two DFT functionals, such as LDA with CA-PZ and GGA with RPBE methods have been performed. The band gaps for GaCuO2 are 0.756, 0.786 and 0.759 eV for the GGA with PBE, GGA with RPBE, and LDA with CA-PZ, respectively, whereas it has garnered after 6% Fe doping (GaCu0.94Fe0.06O2) is at 0.00 eV. And come to think of it, the thermo-electronic and thermophysical properties have been added to endow with the absorption of visible light, thermal stability and thermal state before and after doping which leads to use these crystals in lasers, solar cell even luminescent as optoelectronic materials.
Avijit Dalal, Shyam Murli Manohar Dhar Dwivedi, Chiranjib Ghosh, Rini Lahiri, Mohamed Henini,
Published: 13 February 2021
Journal of Alloys and Compounds, Volume 868; https://doi.org/10.1016/j.jallcom.2021.159178

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Mahmud Hasan, , Unesco Chakma, Tawhidul Islam
Published: 12 January 2021
Molecular Simulation, Volume 47, pp 594-601; https://doi.org/10.1080/08927022.2020.1868456

Abstract:
By executing the Generalised Gradient Approximation (GGA) based on the Pethew Burke Emzerhof (PBE), the structural geometry, electronic band structures, total density of states (DOS), partial density of states (PDOS) and optical properties for both of undoped and doped ZnAg2GeTe4 were investigated. The calculated band gap of ZnAg2GeTe is 1.06 eV, indicating strong photocatalyst for organic pollutants. To explain the photocatalytic effect owing to hybridisation of orbitals, the DOS were simulated to assess the characteristics of 4s, 3d for Zn, 5s, 4d for Ag, 4s, 3d, 4p for Ge and 4s, 5s 4d 5p for Te orbitals travelling from the highest occupied valance bands to the lowest occupied conduction bands. The optical properties, for instance absorption, reflectivity, dielectric function and loss function may be indicated the increased absorption of visible light, as well as corresponds to electronic structure. For better photocatalytic activity, Fe metal was doped by replacing Ge at 7%. After doping, the band gap was decreased from 1.06 eV to 0.09 eV, and DOS was also increased. Nevertheless, optical properties, especially absorption, were also increased which indicates higher photocatalytic activity. It can be concluded that ZnAg2Ge0.93Fe0.07Te4 shows more photocatalytic activity than ZnAg2GeTe4 with the evidences from the band gap and optical properties.
Tawhidul Islam, Ajoy Kumer, Debashis Howlader, Kamal Bikash Chakma, Unesco Chakma
Turkish Computational and Theoretical Chemistry, Volume 4, pp 24-31; https://doi.org/10.33435/tcandtc.674902

Abstract:
The new compounds, Mg(BiO2)4 was synthesized and structurally characterized semiconductor. Due to theoretical investigation for both of Mg(BiO2)4 and Mg(Bi0.91Ge0.083O2)4, computational tools were used. To calculated the electronic band structures, the total density of state, the partial density of state, and optical properties were used Generalized Gradient Approximation (GGA) based on the Perdew–Burke–Ernzerhoff (PBE0) using first principle method for Mg(BiO2)4. The band gap was recorded 0.545 eV which is supported for good semiconductor. The density of states was simulated for evaluating the nature of 3s, 3p for Mg, 6s 6p, 4d, and 2s, 2p for O atoms. Furthermore, the optical properties including absorption, reflection, refractive index, conductivity, dielectric function, and loss function were simulated which can account for the superior absorption of the visible light. The key point of this research to determine the activity of Ge doped by 11.0%, whereas the band gap, density of state, and optical properties were affected. Analysis of the band gap and optical properties of both of Mg (BiO2)4 and Mg(Bi0.91Ge0.083O2)4, the Ge doped shows the high conductivity than undoped.
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