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Electronic Band Structure and Optical response of Spinel SnX_(2)O_(4)(X=Mg,Zn)through Modified Becke-Johnson Potential

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Chinese Physics Letters 2013年第4期30卷 177-180页

作者： A.Manzar G.Murtaza r.khenata S.Muhammad Hayatullah Department of Physics Hazara University MansehraKPKPakistan Materials Modeling Lab Department of PhysicsIslamia College UniversityPeshawarPakistan LPQ3M Laboratory Institute of Science and TechnologyUniversity of MascaraAlgeria Department of Physics and Astronomy King Saud UniversityP.O.Box 2455Riyadh 11451Saudi Arabia

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 *** 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 *** replacement of the cation Mg by Zn leads to a significant reduction in the value of band gap and consequently affects its dependant optical *** variation is of crucial importance for device fabrication in different regions of the spectrum.

关键词： approximation (4) Modified

Electronic and Optical Properties of Spinel GeMg2O4 and GeCd2O4

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Chinese Physics Letters 2013年第12期30卷 134-138页

Oxide spinels have potential applications in optoelectronics and optics *** 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 *** band gap dependent optical parameters such as dielectric constant,refractive index,reflectivity and optical conductivity are calculated and *** replacement of the cation is observed and analyzed for the compounds studied and a prominent change is *** replacement of the cation Mg by Cd reduces the band gap and its dependent optical *** device fabrication in different regions of the spectrum this variation is strongly recommended.

关键词： approximation potential reflectivity

Electronic Band Profile and Optical response of Spinel MgIn_(2)O_(4)through Modified Becke-Johnson Potential

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Chinese Physics Letters 2013年第6期30卷 190-193页

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 *** 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 *** band gap dependent optical parameters such as the dielectric constant,refractive index,reflectivity,optical conductivity,and electron density are *** 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).

关键词： approximation Modified reflectivity

FirstPrincipleCalculations of the Ground and Excited State Properties of rbPbF_(3)

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Chinese Physics Letters 2013年第9期30卷 128-131页

作者： Hayatullah G.Murtaza r.khenata S.Naeem M.N.Khalid S.Mohammad Materials Modeling Lab Hazara UniversityMansehraPakistan Materials Modeling Lab Department of PhysicsIslamia College UniversityPeshawarPakistan LPQ3M Laboratory Institute of Science and TechnologyUniversity of MascaraAlgeria Department of Physics and Astronomy King Saud UniversityP.O.Box 2455Riyadh 11451Saudi Arabia

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 *** exchange correlation effects are included through the generalized gradient and modified Becke–Johnson ex-change *** lattice constant and band gap of the cubic rbPbF 3 decreases with enhanced *** 3 is brittle,elastically anisotropic,and a direct bandgap *** optical properties such as refractive index𝑜(ω),extinction coefficient𝑙(ω),reflectivity𝑆(ω),and optical conductivity𝜏(ω)are predicted.

关键词： potential. material. method.

Investigations of the half-metallic behavior and the magnetic and thermodynamic properties of half-Heusler CoMnTe and ruMnTe compounds: A first-principles study

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Chinese Physics B 2014年第8期23卷 444-451页

作者： T.Djaafri A.Djaafri A.Elias G.Murtaza r.khenata r.Ahmed S.Bin Omran D.rached Department of Physics Faculty of Science Dr Tahar Moulay University Modeling Laboratory Department of Physics Islamia College Peshawar LPQ3M Laboratory Department of Physics Faculty of Science and Technology Mascara University Department of Physics Faculty of Science Universiti Teknologi MalaysiaUTM Skudai Department of Physics and Astronomy College of Science King Saud University Department of Physics Faculty of Science Djillali Liabes University

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.

关键词： half-Heusler alloys half-metallic behavior magnetism thermodynamic properties first principlesmethods

Mechanical and magneto-electronic properties of europium lanthanide-based cubic perovskites EuYO_(3)(Y=Cr, Mn, Fe): An ab initio study

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Journal of rare Earths 2024年第3期42卷 562-569,I0005页

作者： Hayat Ullah Azra Sarwar Sajad Ali rabah khenata Abdelmadjid Bouhemadou Saad Bin-Omran Department of Physics Women University of Azad Jammu&Kashmir Bagh 10250Pakistan Department of Physics Abdul Wali Khan UniversityMardan23200KPPakistan LPQ3M Laboratory Institute of Science and TechnologyUniversity of Mascara29000MascaraAlgeria Laboratory for Developing New Materials and Their Characterization Farhat Abbas University Setif l19000SetifAlgeria Department of Physics and Astronomy College of ScienceKing Saud UniversityP.O.Box 2455Riyadh11451Saudi Arabia

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.

关键词： Perovskites GGA+U Elastic constants Band structure Magnetic moments rare earths

Analysis and Optimization of Operational and Pollutant Attributes of Diesel Engine with CNT-Infused Orange Peel Biodiesel-Diesel Blend Fuel

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Journal of Thermal Science 2024年第2期33卷 761-778页

作者： ranjeet rAI r.r.SAHOO Mechanical Engineering Department GLA UniversityMathura281406India Mechanical Engineering Department IIT(BHU)Varanasi221005India

The current study is performed to find sustainable solutions for the future of transportation and environmental *** conventional methods and experimental design table(L16 Orthogonal Array)techniques have been employed to examine and optimize a diesel-powered engine's operational and pollutant *** L16 Orthogonal Array is obtained through Taguchi's experimental design approach using Minitab 16 *** experimental design incorporated three control variables,namely engine speed,fuel type,and engine load,each with four *** operational parameters,namely brake thermal efficiency(BTE)and brake specific fuel consumption(BSFC),as well as the emission characteristics,including hydrocarbon(HC),carbon monoxide(CO),nitrogen oxide(NO),and smoke emissions,were acquired using the L16 orthogonal array(OA) and subsequently *** utilization of methodologies such as signal-to-noise(S/N) ratio and grey analysis was employed to determine the optimal operational state of the engine to achieve maximum performance while minimizing *** engine's ideal state of operation,in terms of BTE and BSFC,was determined to be at 75% engine load,1000 r/min engine speed,and using 10^(-4)(in vol) carbon nanotube incorporated 20% orange peel biodiesel(OPB20CNT100) blended fuel(A3-B1-C4).The study indicated that engine load significantly influenced BTE and BSFC,with 84.05% and 87.79% contribution factors,*** 25% engine load,1000 r/min,and OPB20CNT100 fuel(A1-B1-C4) CO,smoke,NO,and HC emissions were the *** load affects emissions the *** BSFC increased 3.10% and NO emissions 1.77%.BTE,CO,smoke,and HC emissions decreased by 1.9%,12.29%,47.05%,and 47.22%,respectively,at optimal operating conditions concerning diesel *** study shows that Taguchi-Grey's experimental design optimizes diesel engine operational and pollutant *** outcomes revealed that orange peel biodiesel infused with CNT can replace diesel fuel in a

关键词： Taguchi-Grey method OPB20CNT100 transesterification S/N ratio GrG HC CO and NO

Kinematic analysis of flexible bipedal robotic systems

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Applied Mathematics and Mechanics(English Edition) 2024年第5期45卷 795-818页

作者： r.FAZEL A.M.SHAFEI S.r.NEKOO Department of Mechanical Engineering Shahid Bahonar University of KermanKerman ***Iran Departamento de Ingenieria de Sistemas y Automatica Escuela Técnica Superior de IngenieriaUniversidad de SevillaSeville 41092Spain

In spite of its intrinsic complexities,the passive gait of bipedal robots on a sloping ramp is a subject of interest for numerous *** distinguishes the present research from similar works is the consideration of flexibility in the constituent links of this type of robotic *** is not a far-fetched assumption because in the transient(impact)phase,due to the impulsive forces which are applied to the system,the likelihood of exciting the vibration modes increases ***,the human leg bones that are involved in walking are supported by viscoelastic muscles and ***,for achieving more exact results,it is essential to model the robot links with viscoelastic *** this end,the Gibbs-Appell formulation and Newton's kinematic impact law are used to derive the most general form of the system's dynamic equations in the swing and transient phases of *** most important issue in the passive walking motion of bipedal robots is the determination of the initial robot configuration with which the system could accomplish a periodic and stable gait solely under the effect of gravitational *** extremely unstable nature of the system studied in this paper and the vibrations caused by the impulsive forces induced by the impact of robot feet with the inclined surface are some of the very serious challenges encountered for achieving the above-mentioned *** overcome such challenges,an innovative method that uses a combination of the linearized equations of motion in the swing phase and the algebraic motion equations in the transition phase is presented in this paper to obtain an eigenvalue *** solving this problem,the suitable initial conditions that are necessary for the passive gait of this bipedal robot on a sloping surface are *** effects of the characteristic parameters of elastic links including the modulus of elasticity and the Kelvin-Voigt coefficient on the walking stability of this type of

关键词： bipedal robot flexible link swing phase transient phase eigenvalue problem Kelvin-Voigt coefficient

Holographic dark energy in non-conserved gravity theory

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Communications in Theoretical Physics 2024年第4期76卷 126-133页

作者： H r Fazlollahi Institute of Gravitation and Cosmology Peoples Friendship University of Russia(RUDN University)6 Miklukho-Maklaya StMoscow117198Russia

recently, reconsidering the rastall idea T_(μ;νν)^(v)=α_(,μ) through relativistic thermodynamics gives a new form for the scalar field α which led us to construct modern modified theory of gravity debugged ‘non-conserved gravity theory’ Fazlollahi 2023 Euro. Phys. J. C 83 923. This theory unlike other modified theories of gravity cannot directly explain the current acceleration expansion in the absence of the cosmological constant and or existence of other forms of dark energy. Hence, in this study we have reinvestigated holographic dark energy Ρ_(X)~H^(2) in the non-conserved theory of gravity. In this context, the density and pressure of dark energy depend on the non-conserved term and density of the dust matter field. As shown, due to non-conservation effects on large-scale structures, unlike the original holographic model, our model onsets an acceleration epoch for the current Universe satisfies observations. Moreover, the interaction and viscous scenarios are studied for this model.

关键词： non-conserved gravity covariant form of thermodynamics holographic dark energy