Structural,elastic,electronic,chemical bonding and optical properties of the cubic RbPbF 3 compound under pres-sure are studied using a highly accurate state-of-the-art full potential linearized augmented plane wave m...Structural,elastic,electronic,chemical bonding and optical properties of the cubic RbPbF 3 compound under pres-sure are studied using a highly accurate state-of-the-art full potential linearized augmented plane wave method.The exchange correlation effects are included through the generalized gradient and modified Becke–Johnson ex-change potential.The lattice constant and band gap of the cubic RbPbF 3 decreases with enhanced pressure.RbPbF 3 is brittle,elastically anisotropic,and a direct bandgap material.Its optical properties such as refractive index𝑜(ω),extinction coefficient𝑙(ω),reflectivity𝑆(ω),and optical conductivity𝜏(ω)are predicted.展开更多
Half-Heusler compounds are an impressive class of materials with a huge potential for different applications such as in future energy, especially in the fields of thermoelectrics and solar cells. We present ab fnitio ...Half-Heusler compounds are an impressive class of materials with a huge potential for different applications such as in future energy, especially in the fields of thermoelectrics and solar cells. We present ab fnitio total energy calculations within the modified Becke-Johnson generalized gradient approximation （mBJ-GGA） to obtain the physical properties of SrAlGa compounds. The structural, elastic, acoustic, electronic, chemical bonding, optical, and thermoelectric properties are calculated and compared with the available calculation data. The SrAlGa is found to be a small-band-gap （0.125-0.175 eV） material, suitable for thermoelectric applications with a relatively high Seebeck coefficient. Also, SrAIGa has the potential in the optoelectronic applications due to high optical conductivity and reflectivity in the infrared and visible region of electromagnetic spectra.展开更多
Oxide spinels have potential applications in optoelectronics and optics fields.In this work the electronic band structure and optical properties of GeMg2O4 and GeCd2O4 are calculated by first principles technique base...Oxide spinels have potential applications in optoelectronics and optics fields.In this work the electronic band structure and optical properties of GeMg2O4 and GeCd2O4 are calculated by first principles technique based on the new potential approximation known as the modified Becke-Johnson exchange potential approximation(mBJ).The local density and generalized gradient approximations significantly underestimate the direct band gap values compared to the mBJ.The band gap dependent optical parameters such as dielectric constant,refractive index,reflectivity and optical conductivity are calculated and analyzed.The replacement of the cation is observed and analyzed for the compounds studied and a prominent change is noticed.The replacement of the cation Mg by Cd reduces the band gap and its dependent optical parameters.For device fabrication in different regions of the spectrum this variation is strongly recommended.展开更多
We employ the first-principles technique based on the modified Becke–Johnson(BJ)exchange potential for the prediction of the electronic band structure,optical properties,and electron density of the cubic MgIn_(2)O_(4...We employ the first-principles technique based on the modified Becke–Johnson(BJ)exchange potential for the prediction of the electronic band structure,optical properties,and electron density of the cubic MgIn_(2)O_(4)spinel compound.It is found that the calculated band gap value with the modified BJ approximation is significantly improved over the results based on the generalized gradient approximation and the local density approximation in comparison to the experimental data.The band gap dependent optical parameters such as the dielectric constant,refractive index,reflectivity,optical conductivity,and electron density are predicted.The optical response suggests that MgIn_(2)O_(4)is an applicant material in optoelectronic devices in various parts of the energy spectrum like MgAl_(2)O_(4)and MgGa_(2)O_(4).展开更多
The modified Becke–Johnson exchange potential approximation is applied to predict the band structure,optical parameters and electron density of SnMg_(2)O_(4)and SnZn_(2)O_(4).The local density approximation,generaliz...The modified Becke–Johnson exchange potential approximation is applied to predict the band structure,optical parameters and electron density of SnMg_(2)O_(4)and SnZn_(2)O_(4).The local density approximation,generalized gradient approximation(GGA),EV-GGA significantly underestimate the direct band gap values compared to modified Becke–Johnson approximation.The band gap dependent optical parameters such as dielectric constant,index of refraction,reflectivity,and optical conductivity are calculated and analyzed.A prominent feature of cation replacement is observed and analyzed for these studied compounds.The replacement of the cation Mg by Zn leads to a significant reduction in the value of band gap and consequently affects its dependant optical parameters.This variation is of crucial importance for device fabrication in different regions of the spectrum.展开更多
A first-principles technique capable of describing the nearly excited states of semiconductors and insulators,namely the modified Becke–Johnson(mBJ)potential approximation,is used to investigate the electronic band s...A first-principles technique capable of describing the nearly excited states of semiconductors and insulators,namely the modified Becke–Johnson(mBJ)potential approximation,is used to investigate the electronic band structure and optical properties of spinel oxides:GeZn_(2)O_(4).The predicted band gaps using the mBJ approximation are significantly more accurate than the proposed previous theoretical work using the common LDA and GGA.Band gap dependent optical parameters,like the dielectric constant,index of refraction,reflectivity and optical conductivity are calculated and analyzed.The results from the dielectric constant shows that the numerical value of the static dielectric,after dropping constantly,becomes less than zero and the material exhibits metallic behavior.The refractive index also drops below unity for photons higher than 18 eV,which indicates that the velocities of incident photons are greater than the velocity of light.However,these phenomena can be explained by the fact that a signal must be transmitted as a wave packet rather than a monochromatic wave.This comprehensive theoretical study of the optoelectronic properties predicts that these materials can effectively be used in optical devices.展开更多
A new potential approximation known as modified Becke-Johnson based on density functional theory is applied to compute the electronic band profile and optical response of CdIn2O4, CdGa2O4 and CDAl2O4 compounds. The di...A new potential approximation known as modified Becke-Johnson based on density functional theory is applied to compute the electronic band profile and optical response of CdIn2O4, CdGa2O4 and CDAl2O4 compounds. The direct band gap with common LDA, GGA and EV-GGA is drastically underestimated compared with modified 13ecke-Johnson approximation, whose results are significantly closer to the experimental findings. The optical properties like dielectric constant, refractive index, reflectivity, optical conductivity and absorption coefficient axe also computed. A unique characteristic associated with cation replacement is studied; the replacement of cation In by Ga and Ga by AI significantly reduces the direct energy band gap in these compounds. This variation is of crucial importance for band gap dependent optical properties of these compounds, which is also proof for applications of these compounds in optoelectronic devices.展开更多
In this work the structural,electronic and thermoelectric properties of YbMg_(2)X_(2)(X=P,As,Sb,Bi)zintl compounds were investigated comprehensively using first principles study.The electronic properties were studied ...In this work the structural,electronic and thermoelectric properties of YbMg_(2)X_(2)(X=P,As,Sb,Bi)zintl compounds were investigated comprehensively using first principles study.The electronic properties were studied using PBE GGA,TB-mBJ and hybrid(YS-PBE0)potentials.All the structural parameters of optimized structures are in harmonious agreement to the available data.The band structure study illustrates that the titled materials manifest metallic and semi metallic nature using PBE and TB-mBJ potentials while they show wide band gap semiconducting behavior by following hybrid(YS-PBE0)potential.Total density of states(TDOS)and partial density of states(PDOS)were also calculated to glimpse the contribution of orbitals of atoms in the formation of bands.Transport properties were studied by using BoltzTraP2 code employed to WIEN2k.We get enormous values of Seebeck coefficient(S),power factor(PF)and thermoelectric figure of merit(ZT)for all the samples YbMg_(2)X_(2)(X=P,As,Sb,Bi),Moreover,the overwhelming transport properties for the titled compounds indicate the optimum level of carriers’concentration which pinpoints these materials to be better thermoelectrics in the 1-2-2 zintl family.展开更多
Relaxors exhibit unique dielectric response properties such as diffuse phase transitions and strong dispersion of the dielectric constant.The origin of these properties is still not fully understood.Here,we review our...Relaxors exhibit unique dielectric response properties such as diffuse phase transitions and strong dispersion of the dielectric constant.The origin of these properties is still not fully understood.Here,we review our work on usingfirst-principles-based methods to elucidate the connections between composition,local structure and dynamics in Pb-based relaxors.展开更多
Methods capable of tuning the properties of van der Waals(vdW)layered materials in a controlled and reversible manner are highly desirable.Interfacial electronic properties of two-dimensional vdW heterostructure consi...Methods capable of tuning the properties of van der Waals(vdW)layered materials in a controlled and reversible manner are highly desirable.Interfacial electronic properties of two-dimensional vdW heterostructure consisting of silicene and indium selenide(InSe)have been calculated using density functional theory-based computational code.Furthermore,in order to vary the aforementioned properties,silicene is slid over a InSe layer in the presence of Li intercalation.On intercalation of the heterostructure,the buckling parameter associated with the corrugation of silicene decreases from 0.44A to 0.36A,whereas the InSe structure remains unaffected.Potential energy scans reveal a significant increase in the sliding energy barrier for the case of intercalated heterostructure as compared with the unintercalated heterostructure.The sliding of the silicene encounters the maximum energy barrier of 0.14 eV.Anisotropic analysis shows the noteworthy differences between calculated in-plane and out-of-plane part of dielectric function.A variation of the planar average charge density difference,dipole charge transfer and dipole moment have been discussed to elucidate the usability spectrum of the heterostructure.The employed approach based on intercalation and layer sliding can be effectively utilized for obtaining next-generation multifunctional devices.展开更多
基金Supported by the Deanship of Scientific Research at King Saud University under Grant No RPG-VPP-088.
文摘Structural,elastic,electronic,chemical bonding and optical properties of the cubic RbPbF 3 compound under pres-sure are studied using a highly accurate state-of-the-art full potential linearized augmented plane wave method.The exchange correlation effects are included through the generalized gradient and modified Becke–Johnson ex-change potential.The lattice constant and band gap of the cubic RbPbF 3 decreases with enhanced pressure.RbPbF 3 is brittle,elastically anisotropic,and a direct bandgap material.Its optical properties such as refractive index𝑜(ω),extinction coefficient𝑙(ω),reflectivity𝑆(ω),and optical conductivity𝜏(ω)are predicted.
文摘Half-Heusler compounds are an impressive class of materials with a huge potential for different applications such as in future energy, especially in the fields of thermoelectrics and solar cells. We present ab fnitio total energy calculations within the modified Becke-Johnson generalized gradient approximation （mBJ-GGA） to obtain the physical properties of SrAlGa compounds. The structural, elastic, acoustic, electronic, chemical bonding, optical, and thermoelectric properties are calculated and compared with the available calculation data. The SrAlGa is found to be a small-band-gap （0.125-0.175 eV） material, suitable for thermoelectric applications with a relatively high Seebeck coefficient. Also, SrAIGa has the potential in the optoelectronic applications due to high optical conductivity and reflectivity in the infrared and visible region of electromagnetic spectra.
文摘Oxide spinels have potential applications in optoelectronics and optics fields.In this work the electronic band structure and optical properties of GeMg2O4 and GeCd2O4 are calculated by first principles technique based on the new potential approximation known as the modified Becke-Johnson exchange potential approximation(mBJ).The local density and generalized gradient approximations significantly underestimate the direct band gap values compared to the mBJ.The band gap dependent optical parameters such as dielectric constant,refractive index,reflectivity and optical conductivity are calculated and analyzed.The replacement of the cation is observed and analyzed for the compounds studied and a prominent change is noticed.The replacement of the cation Mg by Cd reduces the band gap and its dependent optical parameters.For device fabrication in different regions of the spectrum this variation is strongly recommended.
基金Supported by the Deanship of Scientific Research at King Saud University under Grant No RPG-VPP-088.
文摘We employ the first-principles technique based on the modified Becke–Johnson(BJ)exchange potential for the prediction of the electronic band structure,optical properties,and electron density of the cubic MgIn_(2)O_(4)spinel compound.It is found that the calculated band gap value with the modified BJ approximation is significantly improved over the results based on the generalized gradient approximation and the local density approximation in comparison to the experimental data.The band gap dependent optical parameters such as the dielectric constant,refractive index,reflectivity,optical conductivity,and electron density are predicted.The optical response suggests that MgIn_(2)O_(4)is an applicant material in optoelectronic devices in various parts of the energy spectrum like MgAl_(2)O_(4)and MgGa_(2)O_(4).
基金the Deanship of Scientific Research at King Saud University under Grant No RPG-VPP-088.
文摘The modified Becke–Johnson exchange potential approximation is applied to predict the band structure,optical parameters and electron density of SnMg_(2)O_(4)and SnZn_(2)O_(4).The local density approximation,generalized gradient approximation(GGA),EV-GGA significantly underestimate the direct band gap values compared to modified Becke–Johnson approximation.The band gap dependent optical parameters such as dielectric constant,index of refraction,reflectivity,and optical conductivity are calculated and analyzed.A prominent feature of cation replacement is observed and analyzed for these studied compounds.The replacement of the cation Mg by Zn leads to a significant reduction in the value of band gap and consequently affects its dependant optical parameters.This variation is of crucial importance for device fabrication in different regions of the spectrum.
文摘A first-principles technique capable of describing the nearly excited states of semiconductors and insulators,namely the modified Becke–Johnson(mBJ)potential approximation,is used to investigate the electronic band structure and optical properties of spinel oxides:GeZn_(2)O_(4).The predicted band gaps using the mBJ approximation are significantly more accurate than the proposed previous theoretical work using the common LDA and GGA.Band gap dependent optical parameters,like the dielectric constant,index of refraction,reflectivity and optical conductivity are calculated and analyzed.The results from the dielectric constant shows that the numerical value of the static dielectric,after dropping constantly,becomes less than zero and the material exhibits metallic behavior.The refractive index also drops below unity for photons higher than 18 eV,which indicates that the velocities of incident photons are greater than the velocity of light.However,these phenomena can be explained by the fact that a signal must be transmitted as a wave packet rather than a monochromatic wave.This comprehensive theoretical study of the optoelectronic properties predicts that these materials can effectively be used in optical devices.
文摘A new potential approximation known as modified Becke-Johnson based on density functional theory is applied to compute the electronic band profile and optical response of CdIn2O4, CdGa2O4 and CDAl2O4 compounds. The direct band gap with common LDA, GGA and EV-GGA is drastically underestimated compared with modified 13ecke-Johnson approximation, whose results are significantly closer to the experimental findings. The optical properties like dielectric constant, refractive index, reflectivity, optical conductivity and absorption coefficient axe also computed. A unique characteristic associated with cation replacement is studied; the replacement of cation In by Ga and Ga by AI significantly reduces the direct energy band gap in these compounds. This variation is of crucial importance for band gap dependent optical properties of these compounds, which is also proof for applications of these compounds in optoelectronic devices.
基金the Deanship of Scientific Research at King Khalid University for funding this work through General Research Project under grant number(R.G.P2/139/43)。
文摘In this work the structural,electronic and thermoelectric properties of YbMg_(2)X_(2)(X=P,As,Sb,Bi)zintl compounds were investigated comprehensively using first principles study.The electronic properties were studied using PBE GGA,TB-mBJ and hybrid(YS-PBE0)potentials.All the structural parameters of optimized structures are in harmonious agreement to the available data.The band structure study illustrates that the titled materials manifest metallic and semi metallic nature using PBE and TB-mBJ potentials while they show wide band gap semiconducting behavior by following hybrid(YS-PBE0)potential.Total density of states(TDOS)and partial density of states(PDOS)were also calculated to glimpse the contribution of orbitals of atoms in the formation of bands.Transport properties were studied by using BoltzTraP2 code employed to WIEN2k.We get enormous values of Seebeck coefficient(S),power factor(PF)and thermoelectric figure of merit(ZT)for all the samples YbMg_(2)X_(2)(X=P,As,Sb,Bi),Moreover,the overwhelming transport properties for the titled compounds indicate the optimum level of carriers’concentration which pinpoints these materials to be better thermoelectrics in the 1-2-2 zintl family.
基金This work was supported by the O±ce of Naval Research,under Grant No.N00014-11-1-0578by the NSF under grant DMR11-20901.Computational support was provided by a Challenge Grant from the HPCMO of the U.S.Department of Defense.
文摘Relaxors exhibit unique dielectric response properties such as diffuse phase transitions and strong dispersion of the dielectric constant.The origin of these properties is still not fully understood.Here,we review our work on usingfirst-principles-based methods to elucidate the connections between composition,local structure and dynamics in Pb-based relaxors.
文摘Methods capable of tuning the properties of van der Waals(vdW)layered materials in a controlled and reversible manner are highly desirable.Interfacial electronic properties of two-dimensional vdW heterostructure consisting of silicene and indium selenide(InSe)have been calculated using density functional theory-based computational code.Furthermore,in order to vary the aforementioned properties,silicene is slid over a InSe layer in the presence of Li intercalation.On intercalation of the heterostructure,the buckling parameter associated with the corrugation of silicene decreases from 0.44A to 0.36A,whereas the InSe structure remains unaffected.Potential energy scans reveal a significant increase in the sliding energy barrier for the case of intercalated heterostructure as compared with the unintercalated heterostructure.The sliding of the silicene encounters the maximum energy barrier of 0.14 eV.Anisotropic analysis shows the noteworthy differences between calculated in-plane and out-of-plane part of dielectric function.A variation of the planar average charge density difference,dipole charge transfer and dipole moment have been discussed to elucidate the usability spectrum of the heterostructure.The employed approach based on intercalation and layer sliding can be effectively utilized for obtaining next-generation multifunctional devices.
