In this study,an experimental analysis for determining the fatigue strength of HDPE-100 under cyclic loading is presented.The curve of cumulative fatigue damage versus number of cycles(D-N)was deduced from stiffness d...In this study,an experimental analysis for determining the fatigue strength of HDPE-100 under cyclic loading is presented.The curve of cumulative fatigue damage versus number of cycles(D-N)was deduced from stiffness degradation.Based on the three stage damage trend,the remaining fatigue life is numerically predicted by considering a double term power damage accumulation model.This model is found to be accurate,both in modeling the rapid damage growth in the early life and near the end of the fatigue life.Numerical results illustrate that the proposed model is capable of accurately fitting several different sets of experimental data.展开更多
Cold expansion is an efficient way to improve the fatigue life of an open hole. In this paper, three finite element models have been established to crack growth from an expanded hole is simulated. Expansion and its de...Cold expansion is an efficient way to improve the fatigue life of an open hole. In this paper, three finite element models have been established to crack growth from an expanded hole is simulated. Expansion and its degree influence are studied using a numerical analysis. Stress intensity factors are determined and used to evaluate the fatigue life. The residual stress field is evaluated using a nonlinear analysis and superposed with the applied stress field in order to estimate fatigue crack growth. Experimental test is conducted under constant loading. The results of this investigation indicate expansion and its degree are a benefit of fatigue life and a good agreement was observed between FEM simulations and experimental results.展开更多
Computational calculations using density functional theory(DFT) were performed for the first time using the full potential linearized augmented plane wave plus local orbital method(FP-LAPW + LO) to determine the struc...Computational calculations using density functional theory(DFT) were performed for the first time using the full potential linearized augmented plane wave plus local orbital method(FP-LAPW + LO) to determine the structural, elastic, electronic and magnetic properties of europium-based cubic perovskites EuYO_(3)(Y=Cr, Mn, Fe). The exchange correlation potentials of GGA along with some analytical methods were adopted for the computation of structural and elastic properties. Moreover, the GGA + U formalism was also added for obtaining more precise electronic and magnetic properties, particularly to address the Eu-4f and Y-3d orientations in the spin-polarized double cell symmetry. The observed lattice parameters of these compounds are consistent with experiment. The observed bulk moduli predict that EuCrO_(3) is harder and less compressible than EuMnO_(3) and EuFeO_(3). The calculated tolerance factors of these compounds are within the cubic symmetry range. Our computed critical radius of EuCrO_(3) shows that EuCrO_(3) has a larger migration energy. Based on their elastic properties, these compounds are ductile in nature. We also computed the thermal properties of these compounds. The band structures and density of states show that these compounds are metallic in character. The lowest ground state energy and magnetic moments of these compounds expose their ferromagnetic nature. The metallic nature and strong ferromagnetism of these compounds make them promising applicants for application in spintronic.展开更多
In this paper,flow of slightly rarefied compressible nitrogen in microchannels has been investigated numerically for low values of Reynolds and Mach numbers.The 2D governing equations were solved using Finite Element ...In this paper,flow of slightly rarefied compressible nitrogen in microchannels has been investigated numerically for low values of Reynolds and Mach numbers.The 2D governing equations were solved using Finite Element Method with first-order slip boundary conditions(Comsol Multiphysics software).A validation was performed by comparing with similar configuration from the literature.It was found that our model can accurately predict the pressure driven flow in microchannels.Several interesting findings are reported about the Relative pressure,longitudinal velocity,Mach number,effect of gas rarefaction and flow rate.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
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
This report presents a first-principles investigation of the structural, electronic, and optical properties of perovskite oxynitrides BaTaO2 N by means of density functional theory（DFT） calculations using the full-p...This report presents a first-principles investigation of the structural, electronic, and optical properties of perovskite oxynitrides BaTaO2 N by means of density functional theory（DFT） calculations using the full-potential linearized augmented plane wave（FP-LAPW） method. Three possible structures（P4mm, I4/mmm, and Pmma） are considered according to the TaO4N2 octahedral configurations. The calculated structural parameters are found to be in good agreement with the previous theoretical and experimental results. Moreover, the electronic band structure dispersion, total, and partial densities of electron states are investigated to explain the origin of bandgaps and the contribution of each orbital＇s species in the valence and the conduction bands. The calculated minimum bandgaps of the P4 mm, I4/mmm, and Pmma structures are 1.83 e V, 1.59 e V, and 1.49 e V, respectively. Furthermore, the optical properties represented by the dielectric functions calculated for BaTaO2 N show that the I4/mmm phase absorbs the light at a large window in both the visible and UV regions,whereas the other two structures（P4mm and Pmma） are more active in the UV region. Our investigations provide important information for the potential application of this material.展开更多
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
First-principles spin-polarized density functional theory （DFT） investigations of the structural, electronic, magnetic, and thermodynamics characteristics of the half-Heusler, CoMnTe and RuMnTe compounds are carried...First-principles spin-polarized density functional theory （DFT） investigations of the structural, electronic, magnetic, and thermodynamics characteristics of the half-Heusler, CoMnTe and RuMnTe compounds are carried out. Calculations are accomplished within a state of the art full-potential （FP） linearized （L） augmented plane wave plus a local orbital （APW ＋ lo） computational approach framed within DFT. The generalized gradient approximation （GGA） parameterized by Perdew, Burke, and Ernzerhof （PBE） is implemented as an exchange correlation functional as a part of the total energy calculation. From the analysis of the calculated electronic band structure as well as the density of states for both compounds, a strong hybridization between d states of the higher valent transition metal （TM） atoms （Co, Ru） and lower valent TM atoms of （Mn） is observed. Furthermore, total and partial density of states （PDOS） of the ground state and the results of spin magnetic moments reveal that these compounds are both stable and ideal half-metallic ferromagnetic. The effects of the unit cell volume on the magnetic properties and half-metaliicity are crucial. It is worth noting that our computed results of the total spin magnetic moments, for CoMnTe equal to 4 ~tB and 3 p-B per unit cell for RuMnTe, nicely follow the rule μ2tot = Zt - 18. Using the quasi-harmonic Debye model, which considers the phononic effects, the effecs of pressure P and temperature T on the lattice parameter, bulk modulus, thermal expansion coefficient, Debye temperature, and heat capacity for these compounds are investigated for the first time.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
In this paper, we investigated the structural, electronic and optical properties of InAs, InN and InP binary compounds and their related ternary and quaternary alloys by using the full potential linearized augmented p...In this paper, we investigated the structural, electronic and optical properties of InAs, InN and InP binary compounds and their related ternary and quaternary alloys by using the full potential linearized augmented plane wave（FP-LAPW）method based on density functional theory（DFT）. The total energies, the lattice parameters, and the bulk modulus and its first pressure derivative were calculated using different exchange correlation approximations. The local density approach（LDA） and Tran–Blaha modified Becke–Johnson（TB-m BJ） approximations were used to calculate the band structure.Nonlinear variations of the lattice parameters, the bulk modulus and the band gap with compositions x and y are found.Furthermore, the optical properties and the dielectric function, refractive index and loss energy were computed. Our results are in good agreement with the validated experimental and theoretical data found in the literature.展开更多
A theoretical study of the structural, elastic, electronic, mechanical, and thermal properties of the perovskite-type hydride CaNiH3 is presented. This study is carded out via first-principles full potential （FP） li...A theoretical study of the structural, elastic, electronic, mechanical, and thermal properties of the perovskite-type hydride CaNiH3 is presented. This study is carded out via first-principles full potential （FP） linearized augmented plane wave plus local orbital （LAPW＋lo） method designed within the density functional theory （DFT）. To treat the exchange-correlation energy/potential for the total energy calculations, the local density approximation （LDA） of Perdew-Wang （PW） and the generalized gradient approximation （GGA） of Perdew-Burke-Ernzerhof （PBE） are used. The three independent elastic constants （C11, C12, and C44） are calculated from the direct computation of the stresses generated by small strains. Besides, we report the variation of the elastic constants as a function of pressure as well. From the calculated elastic constants, the mechanical character of CaNiH3 is predicted. Pertaining to the thermal properties, the Debye temperature is estimated from the average sound velocity. To further comprehend this compound, the quasi-harmonic Debye model is used to analyze the thermal properties. From the calculations, we find that the obtained results of the lattice constant （ao）, bulk modulus （Bo）, and its pressure derivative （B0′） are in good agreement with the available theoretical as well as experimental results. Similarly, the obtained electronic band structure demonstrates the metallic character of this perovskite-type hydride.展开更多
The structural,electronic,and magnetic properties of the Nd-doped Rare earth aluminate,La1-xNdxAlO3（x = 0%to 100%） alloys are studied using the full potential linearized augmented plane wave（FP-LAPW） method within...The structural,electronic,and magnetic properties of the Nd-doped Rare earth aluminate,La1-xNdxAlO3（x = 0%to 100%） alloys are studied using the full potential linearized augmented plane wave（FP-LAPW） method within the density functional theory.The effects of the Nd substitution in La AlO3 are studied using the supercell calculations.The computed electronic structure with the modified Becke–Johnson（m BJ） potential based approximation indicates that the La1-xNdxAlO3 alloys may possess half-metallic（HM） behaviors when doped with Nd of a finite density of states at the Fermi level（EF）.The direct and indirect band gaps are studied each as a function of x which is the concentration of Nddoped La AlO3.The calculated magnetic moments in the La1-xNdxAlO3 alloys are found to arise mainly from the Nd-4f state.A probable half-metallic nature is suggested for each of these systems with supportive integral magnetic moments and highly spin-polarized electronic structures in these doped systems at EF.The observed decrease of the band gap with the increase in the concentration of Nd doping in La AlO3 is a suitable technique for harnessing useful spintronic and magnetic 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 paper,single-phase homogeneous nanofluid model is proposed to investigate the natural convection of magneto-hydrodynamic(MIID)flow of Newtonian Cu—H20 nanoliquid in a baffled U-shaped enclosure.The Brinkman m...In this paper,single-phase homogeneous nanofluid model is proposed to investigate the natural convection of magneto-hydrodynamic(MIID)flow of Newtonian Cu—H20 nanoliquid in a baffled U-shaped enclosure.The Brinkman model and Wasp model are considered to measure the effective dynamic viscosity and effective thermal conductivity of the nanoliquid coreespondingly.Nanoliquid's effective properties such as specific heat,density and thermal expansion coefficient are modeled using mixture theory.The complicated PDS(partial differential system)is treated for numeric solutions via the Galerkin finite element method.The pertinent parameters Hartmann number(1≤Ha≤60),Rayleigh number(10^(3)≤Ra≤10^(6))and nanoparticles volume fraction(0%≤Ф≤4%)are taken for the parametric analysis,and it is conducted via streamlines and isotherms.Excellent agreement between numerical results and open literature.It is ascertained that heat transfer rate enhances with Rayleigh number Ra and volume fraction 0,however it is diminished for laiger Hartmann number Ha.展开更多
文摘In this study,an experimental analysis for determining the fatigue strength of HDPE-100 under cyclic loading is presented.The curve of cumulative fatigue damage versus number of cycles(D-N)was deduced from stiffness degradation.Based on the three stage damage trend,the remaining fatigue life is numerically predicted by considering a double term power damage accumulation model.This model is found to be accurate,both in modeling the rapid damage growth in the early life and near the end of the fatigue life.Numerical results illustrate that the proposed model is capable of accurately fitting several different sets of experimental data.
文摘Cold expansion is an efficient way to improve the fatigue life of an open hole. In this paper, three finite element models have been established to crack growth from an expanded hole is simulated. Expansion and its degree influence are studied using a numerical analysis. Stress intensity factors are determined and used to evaluate the fatigue life. The residual stress field is evaluated using a nonlinear analysis and superposed with the applied stress field in order to estimate fatigue crack growth. Experimental test is conducted under constant loading. The results of this investigation indicate expansion and its degree are a benefit of fatigue life and a good agreement was observed between FEM simulations and experimental results.
基金Project supported by the Higher Education of Pakistan Under National Research Grant Program(NRPU)(Grant No:14408/NRPU/R&D/HEC/20212021)。
文摘Computational calculations using density functional theory(DFT) were performed for the first time using the full potential linearized augmented plane wave plus local orbital method(FP-LAPW + LO) to determine the structural, elastic, electronic and magnetic properties of europium-based cubic perovskites EuYO_(3)(Y=Cr, Mn, Fe). The exchange correlation potentials of GGA along with some analytical methods were adopted for the computation of structural and elastic properties. Moreover, the GGA + U formalism was also added for obtaining more precise electronic and magnetic properties, particularly to address the Eu-4f and Y-3d orientations in the spin-polarized double cell symmetry. The observed lattice parameters of these compounds are consistent with experiment. The observed bulk moduli predict that EuCrO_(3) is harder and less compressible than EuMnO_(3) and EuFeO_(3). The calculated tolerance factors of these compounds are within the cubic symmetry range. Our computed critical radius of EuCrO_(3) shows that EuCrO_(3) has a larger migration energy. Based on their elastic properties, these compounds are ductile in nature. We also computed the thermal properties of these compounds. The band structures and density of states show that these compounds are metallic in character. The lowest ground state energy and magnetic moments of these compounds expose their ferromagnetic nature. The metallic nature and strong ferromagnetism of these compounds make them promising applicants for application in spintronic.
文摘In this paper,flow of slightly rarefied compressible nitrogen in microchannels has been investigated numerically for low values of Reynolds and Mach numbers.The 2D governing equations were solved using Finite Element Method with first-order slip boundary conditions(Comsol Multiphysics software).A validation was performed by comparing with similar configuration from the literature.It was found that our model can accurately predict the pressure driven flow in microchannels.Several interesting findings are reported about the Relative pressure,longitudinal velocity,Mach number,effect of gas rarefaction and flow rate.
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.
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This report presents a first-principles investigation of the structural, electronic, and optical properties of perovskite oxynitrides BaTaO2 N by means of density functional theory（DFT） calculations using the full-potential linearized augmented plane wave（FP-LAPW） method. Three possible structures（P4mm, I4/mmm, and Pmma） are considered according to the TaO4N2 octahedral configurations. The calculated structural parameters are found to be in good agreement with the previous theoretical and experimental results. Moreover, the electronic band structure dispersion, total, and partial densities of electron states are investigated to explain the origin of bandgaps and the contribution of each orbital＇s species in the valence and the conduction bands. The calculated minimum bandgaps of the P4 mm, I4/mmm, and Pmma structures are 1.83 e V, 1.59 e V, and 1.49 e V, respectively. Furthermore, the optical properties represented by the dielectric functions calculated for BaTaO2 N show that the I4/mmm phase absorbs the light at a large window in both the visible and UV regions,whereas the other two structures（P4mm and Pmma） are more active in the UV region. Our investigations provide important information for the potential application of this material.
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.
基金financial support provided by the Deanship of Scientific Research at King Saud University for funding this work through research group project No: RPG-VPP-088
文摘First-principles spin-polarized density functional theory （DFT） investigations of the structural, electronic, magnetic, and thermodynamics characteristics of the half-Heusler, CoMnTe and RuMnTe compounds are carried out. Calculations are accomplished within a state of the art full-potential （FP） linearized （L） augmented plane wave plus a local orbital （APW ＋ lo） computational approach framed within DFT. The generalized gradient approximation （GGA） parameterized by Perdew, Burke, and Ernzerhof （PBE） is implemented as an exchange correlation functional as a part of the total energy calculation. From the analysis of the calculated electronic band structure as well as the density of states for both compounds, a strong hybridization between d states of the higher valent transition metal （TM） atoms （Co, Ru） and lower valent TM atoms of （Mn） is observed. Furthermore, total and partial density of states （PDOS） of the ground state and the results of spin magnetic moments reveal that these compounds are both stable and ideal half-metallic ferromagnetic. The effects of the unit cell volume on the magnetic properties and half-metaliicity are crucial. It is worth noting that our computed results of the total spin magnetic moments, for CoMnTe equal to 4 ~tB and 3 p-B per unit cell for RuMnTe, nicely follow the rule μ2tot = Zt - 18. Using the quasi-harmonic Debye model, which considers the phononic effects, the effecs of pressure P and temperature T on the lattice parameter, bulk modulus, thermal expansion coefficient, Debye temperature, and heat capacity for these compounds are investigated for the first time.
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.
基金supported by the Deanship of Scientific Research at King Saud University Group(Grant No.PRG-1437-39)
文摘In this paper, we investigated the structural, electronic and optical properties of InAs, InN and InP binary compounds and their related ternary and quaternary alloys by using the full potential linearized augmented plane wave（FP-LAPW）method based on density functional theory（DFT）. The total energies, the lattice parameters, and the bulk modulus and its first pressure derivative were calculated using different exchange correlation approximations. The local density approach（LDA） and Tran–Blaha modified Becke–Johnson（TB-m BJ） approximations were used to calculate the band structure.Nonlinear variations of the lattice parameters, the bulk modulus and the band gap with compositions x and y are found.Furthermore, the optical properties and the dielectric function, refractive index and loss energy were computed. Our results are in good agreement with the validated experimental and theoretical data found in the literature.
基金the Deanship of Scientific Research at King Saud University for funding the Prolific Research Group (PRG-1437-39)
文摘A theoretical study of the structural, elastic, electronic, mechanical, and thermal properties of the perovskite-type hydride CaNiH3 is presented. This study is carded out via first-principles full potential （FP） linearized augmented plane wave plus local orbital （LAPW＋lo） method designed within the density functional theory （DFT）. To treat the exchange-correlation energy/potential for the total energy calculations, the local density approximation （LDA） of Perdew-Wang （PW） and the generalized gradient approximation （GGA） of Perdew-Burke-Ernzerhof （PBE） are used. The three independent elastic constants （C11, C12, and C44） are calculated from the direct computation of the stresses generated by small strains. Besides, we report the variation of the elastic constants as a function of pressure as well. From the calculated elastic constants, the mechanical character of CaNiH3 is predicted. Pertaining to the thermal properties, the Debye temperature is estimated from the average sound velocity. To further comprehend this compound, the quasi-harmonic Debye model is used to analyze the thermal properties. From the calculations, we find that the obtained results of the lattice constant （ao）, bulk modulus （Bo）, and its pressure derivative （B0′） are in good agreement with the available theoretical as well as experimental results. Similarly, the obtained electronic band structure demonstrates the metallic character of this perovskite-type hydride.
基金Project supported by the DST-SERB,Dy(Grant No.SERB/3586/2013-14)the UGCBSR,FRPS(Grant No.F.30-52/2014)+2 种基金the UGC(New Delhi,India)Inspire Fellowship DST(India)the Deanship of Scientific Research at King Saud University(Grant No.RPG-VPP-088)M P Ghimire thanks the Alexander von Humboldt Foundation,Germany for the financial support
文摘The structural,electronic,and magnetic properties of the Nd-doped Rare earth aluminate,La1-xNdxAlO3（x = 0%to 100%） alloys are studied using the full potential linearized augmented plane wave（FP-LAPW） method within the density functional theory.The effects of the Nd substitution in La AlO3 are studied using the supercell calculations.The computed electronic structure with the modified Becke–Johnson（m BJ） potential based approximation indicates that the La1-xNdxAlO3 alloys may possess half-metallic（HM） behaviors when doped with Nd of a finite density of states at the Fermi level（EF）.The direct and indirect band gaps are studied each as a function of x which is the concentration of Nddoped La AlO3.The calculated magnetic moments in the La1-xNdxAlO3 alloys are found to arise mainly from the Nd-4f state.A probable half-metallic nature is suggested for each of these systems with supportive integral magnetic moments and highly spin-polarized electronic structures in these doped systems at EF.The observed decrease of the band gap with the increase in the concentration of Nd doping in La AlO3 is a suitable technique for harnessing useful spintronic and magnetic 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 Algerian Ministry of Higher Education and Scientific Research through PRFU project no B00L02UN210120180002the General Directorate of Scientific Research and Technological Development(DGRSDT),Algeria.
文摘In this paper,single-phase homogeneous nanofluid model is proposed to investigate the natural convection of magneto-hydrodynamic(MIID)flow of Newtonian Cu—H20 nanoliquid in a baffled U-shaped enclosure.The Brinkman model and Wasp model are considered to measure the effective dynamic viscosity and effective thermal conductivity of the nanoliquid coreespondingly.Nanoliquid's effective properties such as specific heat,density and thermal expansion coefficient are modeled using mixture theory.The complicated PDS(partial differential system)is treated for numeric solutions via the Galerkin finite element method.The pertinent parameters Hartmann number(1≤Ha≤60),Rayleigh number(10^(3)≤Ra≤10^(6))and nanoparticles volume fraction(0%≤Ф≤4%)are taken for the parametric analysis,and it is conducted via streamlines and isotherms.Excellent agreement between numerical results and open literature.It is ascertained that heat transfer rate enhances with Rayleigh number Ra and volume fraction 0,however it is diminished for laiger Hartmann number Ha.
