Theoretical studies of the cubic perovskite CaFeO3 are performed using the full potential linearized augmented plane-wave method with GGA+U.The calculated structural parameters are consistent with the experimental res...Theoretical studies of the cubic perovskite CaFeO3 are performed using the full potential linearized augmented plane-wave method with GGA+U.The calculated structural parameters are consistent with the experimental results.The tolerance factor reveals the cubic phase of the compound.The spin polarized electronic band structures and densities of states as well as the integer value of the magnetic moment of the unit cell(4μB)demonstrate that CaFeO_(3)is half metal.Ferromagnetism in CaFeO_(3)is due to Fe^(+4)–O^(2)–Fe^(+4)superexchange interaction.The robust properties of the compound show that with their compression up to a certain critical lattice constant,known as the robust transition lattice constant,an abrupt change in the electronic and magnetic properties occurs;the compounds lose their integer magnetic moment and become metallic.展开更多
The Western tragopan(Tragopan melanocephalus)is recorded in the IUCN Red List of 2017 as a vulnerable bird species in Pakistan.This study provides valuable information for the conservation of Western tragopan,which is...The Western tragopan(Tragopan melanocephalus)is recorded in the IUCN Red List of 2017 as a vulnerable bird species in Pakistan.This study provides valuable information for the conservation of Western tragopan,which is a globally threatened avian flagship species in Pakistan.This study was conducted to investigate and resolve the conservation challenges surrounding the species in two major habitat zones-Salkhala Game Reserve and Machiara National Park.The study was implemented in May-June 2020 for population density using call count data.Also,questionnaire was used for local residents’perceptions and habitat suitability modeling map was generated using the MaxEnt model based on previously recorded occurrence points as well as recorded in the survey.A total of 26 western Tragopans were identified by call count during the sampling period.Moreover,about 77.3%cited Western Tragopan they more likely to hunt while the remaining 22.6%locals recorded other pheasant.About 45.3%of this hunting for fun but only 22%for economic values and only 3%of people consider hunting as a part of their culture.Results of modeling habitat suitability of the Western tragopan showed that the species suitable habitats are small and patchy in Pakistan.We found that the Normalized Difference Vegetation Index(NDVI)with 40.6 percent contribution was the most important variable in shaping the species distribution.Our model identified some new suitable patches which can be the target of future field monitoring for finding new populations of the species and future conservation planning.展开更多
Structural geometry, electronic band gaps, density of states, optical and mechanical properties of double perovskite halides Cs2InBiX6(X = F, Cl, Br, I) are investigated using the density functional theory. These comp...Structural geometry, electronic band gaps, density of states, optical and mechanical properties of double perovskite halides Cs2InBiX6(X = F, Cl, Br, I) are investigated using the density functional theory. These compounds possess genuine perovskite stoichiometry, evaluated using various geometry-based indices like tolerance factor, octahedral factor, and formation energy. The fundamental electronic band gaps are direct and valued in the range 0.80–2.79 e V. These compounds have narrow band gaps(except Cs2InBiX6) due to strong orbital coupling of the cations. The valence band maximum and conduction band minimum are confirmed to be essentially of In 5 s and Bi 6 p characters, respectively. The splitting of Bi 6 p bands due to strong spin-orbit coupling causes reduction in the band gaps. These compounds have large dispersion in their bands and very low carrier effective masses. The substitution of halogen atoms has great influence on the optical properties. The mechanical properties reveal that Cs2InBiX6(X = F, Cl, Br, I) satisfy the stability criteria in cubic structures.展开更多
Zinc telluride is a versatile wide band gap semiconductor used in many applications.But it has certain limitations like large dimensions and large band gaps.Introducing alkali metal to its bulk lattice(3D)can reduce i...Zinc telluride is a versatile wide band gap semiconductor used in many applications.But it has certain limitations like large dimensions and large band gaps.Introducing alkali metal to its bulk lattice(3D)can reduce its dimensions and lanthanide can produce a red shift in the energy gap by converting it into quaternary compounds.The alkali and lanthanide incorporated quaternary zinc tellurides CsLnZnTe_(3)(Ln=La,Pr,Nd and Sm)form layered crystal structure in which_(∞)^(2)[LnZnTe_(3)]-layers are separated by Cs+layer.The famous lanthanide contraction is experimental both from lattice constants and bond lengths.The calculated band gaps are 2.26,2.28,2.12,2.05 eV for CsLaZnTe_(3),CsPrZnTe_(3),CsNdZnTe_(3) and CsSmZnTe_(3),respectively.These compounds show direct band gap nature.The energy band gaps of these compounds have not been evaluated yet both experimentally and theoretically.Energy loss functions,refractive index and dielectric functions were also calculated to explore the potential applications of CsLnZnTe_(3) in optoelectronic devices.展开更多
Hybrid density functional theory was used to investigate the structural,electronic,magnetic and elastic properties of the Laves phase binary intermetallics RFe_(2)(R=La,Ce,Pr and Nd) in C_(15) crystal structure.The ca...Hybrid density functional theory was used to investigate the structural,electronic,magnetic and elastic properties of the Laves phase binary intermetallics RFe_(2)(R=La,Ce,Pr and Nd) in C_(15) crystal structure.The calculated lattice constants of these materials are found in good agreement with the experiments.The band structures and density of states distribution confirm the metallic nature of all these intermetallics.The optimized energies in different magnetic phases and magnetic susceptibilities by postDFT treatments confirm that all the understudy compounds are ferromagnetic in nature.Elastic parameters were calculated from the cubic elastic coefficients C_(11),C_(12) and C_(44).The elastic properties reveal that these intermetallics are incompressible,ductile,elastically anisotropic and mechanically stable.Based on the metallic nature and ferromagnetic properties,it is expected that these intermetallics are suitable materials for spintronic technology.展开更多
This paper demonstrates the structural, vibrational and photoluminescence characteristics of(ZnO)(VO)(x = 0, 3, 6 and 9 mol%) composites semiconductor synthesized by using the solid state reaction method. X-ray diffra...This paper demonstrates the structural, vibrational and photoluminescence characteristics of(ZnO)(VO)(x = 0, 3, 6 and 9 mol%) composites semiconductor synthesized by using the solid state reaction method. X-ray diffraction(XRD) studies show that(ZnO)(VO)composites have the poly crystalline wurtzite structure of hexagonal Zn O. It is found from the XRD results that the lattice constants and the crystallite size increase while the dislocation density decreases with increase in doping concentration. The existence of E1(TO) and E2(high) Raman modes show that the Zn O still preserve wurtzite structure after doping vanadium oxide, which is in agreement with XRD results. Room temperature photoluminescence(PL) exhibit near band edge and broad deep level emission while indicating the suppression of deep level emission with the incorporation of VOup to a certain concentration(x < 9). Moreover, the optical band gap increase with doping, which is accompanied by the blue shift of the NBE emission.展开更多
文摘Theoretical studies of the cubic perovskite CaFeO3 are performed using the full potential linearized augmented plane-wave method with GGA+U.The calculated structural parameters are consistent with the experimental results.The tolerance factor reveals the cubic phase of the compound.The spin polarized electronic band structures and densities of states as well as the integer value of the magnetic moment of the unit cell(4μB)demonstrate that CaFeO_(3)is half metal.Ferromagnetism in CaFeO_(3)is due to Fe^(+4)–O^(2)–Fe^(+4)superexchange interaction.The robust properties of the compound show that with their compression up to a certain critical lattice constant,known as the robust transition lattice constant,an abrupt change in the electronic and magnetic properties occurs;the compounds lose their integer magnetic moment and become metallic.
文摘The Western tragopan(Tragopan melanocephalus)is recorded in the IUCN Red List of 2017 as a vulnerable bird species in Pakistan.This study provides valuable information for the conservation of Western tragopan,which is a globally threatened avian flagship species in Pakistan.This study was conducted to investigate and resolve the conservation challenges surrounding the species in two major habitat zones-Salkhala Game Reserve and Machiara National Park.The study was implemented in May-June 2020 for population density using call count data.Also,questionnaire was used for local residents’perceptions and habitat suitability modeling map was generated using the MaxEnt model based on previously recorded occurrence points as well as recorded in the survey.A total of 26 western Tragopans were identified by call count during the sampling period.Moreover,about 77.3%cited Western Tragopan they more likely to hunt while the remaining 22.6%locals recorded other pheasant.About 45.3%of this hunting for fun but only 22%for economic values and only 3%of people consider hunting as a part of their culture.Results of modeling habitat suitability of the Western tragopan showed that the species suitable habitats are small and patchy in Pakistan.We found that the Normalized Difference Vegetation Index(NDVI)with 40.6 percent contribution was the most important variable in shaping the species distribution.Our model identified some new suitable patches which can be the target of future field monitoring for finding new populations of the species and future conservation planning.
文摘Structural geometry, electronic band gaps, density of states, optical and mechanical properties of double perovskite halides Cs2InBiX6(X = F, Cl, Br, I) are investigated using the density functional theory. These compounds possess genuine perovskite stoichiometry, evaluated using various geometry-based indices like tolerance factor, octahedral factor, and formation energy. The fundamental electronic band gaps are direct and valued in the range 0.80–2.79 e V. These compounds have narrow band gaps(except Cs2InBiX6) due to strong orbital coupling of the cations. The valence band maximum and conduction band minimum are confirmed to be essentially of In 5 s and Bi 6 p characters, respectively. The splitting of Bi 6 p bands due to strong spin-orbit coupling causes reduction in the band gaps. These compounds have large dispersion in their bands and very low carrier effective masses. The substitution of halogen atoms has great influence on the optical properties. The mechanical properties reveal that Cs2InBiX6(X = F, Cl, Br, I) satisfy the stability criteria in cubic structures.
基金the Deanship of Scientific Research at King Khalid University for funding this work through research groups program under grant number(RGP.2/141/43)。
文摘Zinc telluride is a versatile wide band gap semiconductor used in many applications.But it has certain limitations like large dimensions and large band gaps.Introducing alkali metal to its bulk lattice(3D)can reduce its dimensions and lanthanide can produce a red shift in the energy gap by converting it into quaternary compounds.The alkali and lanthanide incorporated quaternary zinc tellurides CsLnZnTe_(3)(Ln=La,Pr,Nd and Sm)form layered crystal structure in which_(∞)^(2)[LnZnTe_(3)]-layers are separated by Cs+layer.The famous lanthanide contraction is experimental both from lattice constants and bond lengths.The calculated band gaps are 2.26,2.28,2.12,2.05 eV for CsLaZnTe_(3),CsPrZnTe_(3),CsNdZnTe_(3) and CsSmZnTe_(3),respectively.These compounds show direct band gap nature.The energy band gaps of these compounds have not been evaluated yet both experimentally and theoretically.Energy loss functions,refractive index and dielectric functions were also calculated to explore the potential applications of CsLnZnTe_(3) in optoelectronic devices.
文摘Hybrid density functional theory was used to investigate the structural,electronic,magnetic and elastic properties of the Laves phase binary intermetallics RFe_(2)(R=La,Ce,Pr and Nd) in C_(15) crystal structure.The calculated lattice constants of these materials are found in good agreement with the experiments.The band structures and density of states distribution confirm the metallic nature of all these intermetallics.The optimized energies in different magnetic phases and magnetic susceptibilities by postDFT treatments confirm that all the understudy compounds are ferromagnetic in nature.Elastic parameters were calculated from the cubic elastic coefficients C_(11),C_(12) and C_(44).The elastic properties reveal that these intermetallics are incompressible,ductile,elastically anisotropic and mechanically stable.Based on the metallic nature and ferromagnetic properties,it is expected that these intermetallics are suitable materials for spintronic technology.
文摘This paper demonstrates the structural, vibrational and photoluminescence characteristics of(ZnO)(VO)(x = 0, 3, 6 and 9 mol%) composites semiconductor synthesized by using the solid state reaction method. X-ray diffraction(XRD) studies show that(ZnO)(VO)composites have the poly crystalline wurtzite structure of hexagonal Zn O. It is found from the XRD results that the lattice constants and the crystallite size increase while the dislocation density decreases with increase in doping concentration. The existence of E1(TO) and E2(high) Raman modes show that the Zn O still preserve wurtzite structure after doping vanadium oxide, which is in agreement with XRD results. Room temperature photoluminescence(PL) exhibit near band edge and broad deep level emission while indicating the suppression of deep level emission with the incorporation of VOup to a certain concentration(x < 9). Moreover, the optical band gap increase with doping, which is accompanied by the blue shift of the NBE emission.
