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Electronic and thermoelectric properties of alkali metal-based perovskites CsYbF3 and RbYbF3

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Chinese Physics B 2020年第11期29卷 473-478页

作者： Q Mahmood n A noor T Ghrib nessrin A Kattan Asif Mahmood Shahid M Ramay Basic and Applied Scientific Research Center Imam Abdulrahman Bin Faisal UniversityP.O.Box 198231441DammamSaudi Arabia Department of Physics College of ScienceImam Abdulrahman Bin Faisal UniversityP.O.Box 198231441DammamSaudi Arabia Department of Physics Riphah International UniversityLahorePakistan Department of Physics Faculty of ScienceTaibah UniversityMedinaSaudi Arabia Chemical Engineering Department College of EngineeringKing Saud UniversityRiyadhSaudi Arabia Physics and Astronomy Department College of ScienceKing Saud University RiyadhRiyadhSaudi Arabia

The electronic and thermoelectric properties of alkali metal-based fluorides CsYbF3 and RbYbF3 are studied by using Wien2k and BoltzTraP *** structural and thermodynamic stability of these materials are confirmed by tolerance factor(0.94 and 0.99 for RbYbF3 and CsYbF3)and negative formation *** optimized lattice constants and bulk moduli are consistent with the results reported in the *** reported band gap for RbYbF3 is 0.86 eV which decreases to 0.83 eV by the replacement of Cs with *** electrical and thermal conductivities along with Seebeck coefficients decrease with temperature rising from 0 K to 800 *** large values of thermoelectric parameters for positive chemical potentials show that the character is dominated by *** studied materials have figures of merit 0.82 and 0.81 at room temperature respectively,for RbYbF3 and CsYbF3 and increase with temperature ***,the materials under study may have potential application values in thermoelectric generators and refrigerators.

关键词： density functional theory thermodynamic stability electrical conductivity figure of merit

Investigations of mechanical, electronic, and magnetic properties of non-magnetic MgTe and ferro-magnetic Mg_(0.75)T M_(0.25)Te (TM = Fe, Co, ni): An ab-initio calculation

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Chinese Physics B 2016年第4期25卷 303-313页

作者： Mahmood Q Alay-e-Abbas S M Mahmood I Asif Mahmood noor n a Department of Physics University of the Punjab Quaid-e-Azam Campus Department of Physics Government College University Faisalabad Department of Physics University of Sargodha Centre for High Energy Physics University of the Punjab Quaid-e-Azam Campus College of Engineering Chemical Engineering Department King Saud University

The mechanical, electronic and magnetic properties of non-magnetic MgTe and ferro-magnetic （FM） Mgo.75 TM025 Te （TM = Fe, Co, ni） in the zinc-blende phase are studied by ab-initio calculations for the first time. We use the generalized gradient approximation functional for computing the structural stability, and mechanical properties, while the modified Becke and Johnson local （spin） density approximation （mBJLDA） is utilized for determining the electronic and magnetic properties. By comparing the energies of non-magnetic and FM calculations, we find that the compounds are stable in the FM phase, which is confirmed by their structural stabilities in terms of enthalpy of formation. Detailed descriptions of elastic properties of Mgo.75TMo.25Te alloys in the FM phase are also presented. For electronic properties, the spin- polarized electronic band structures and density of states are computed, showing that these compounds are direct bandgap materials with strong hybridizations of TM 3d states and Te p states. Further, the ferromagnetism is discussed in terms of the Zener free electron model, RKKY model and double exchange model. The charge density contours in the （110） plane are calculated to study bonding properties. The spin exchange splitting and crystal field splitting energies are also calculated. The distribution of electron spin density is employed in computing the magnetic moments appearing at the magnetic sites （Fe, Co, ni）, as well as at the non-magnetic sites （Mg, Te）. It is found that the p-d hybridization causes not only magnetic moments on the magnetic sites but also induces negligibly small magnetic moments at the non-magnetic sites.

关键词： FP-LAPW + lo elastic parameters spin polarized electronic properties magnetic properties

Bandgap engineering to tune the optical properties of Be_xMg_(1-x)X(X=S, Se, Te) alloys

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Chinese Physics B 2018年第1期27卷 415-423页

作者： B Sabir n A noor M Rashid Fasih Ud Din Shahid M Ramay Asif Mahmood Centre for Advanced Studies in Physics Government College University Department of Physics School of Science University of Management and TechnologyLahore Pakistan Department of Physics COMSATS Institute of Information Technology Physics and Astronomy Department College of Science King Saud University Chemical Engineering Department College of Engineering King Saud University

Structural, electronic, and optical properties of alloys BexMgl-xX （X = S, Se, Te） in the assortment 0 〈 x 〈 1 were theoretically reported for the first time in zinc-blende （ZB） phase. The calculations were carried out by using full-potential linearized augmented plane wave plus local orbitals （FP-LAPW＋lo） formalism contained by the framework of density functional theory （DFT）. Wu--Cohen （WC） generalized gradient approximation （GGA）, based on optimization energy, has been applied to calculate these theoretical results. In addition, we used Becke and Johnson （mBJ-GGA） potential, modified form of GGA functional, to calculate electronic structural properties up to a high precision degree. The alloys were composed with the concentrations x = 0.25, 0.5, and 0.75 in pursuance of ＇special quasi-random structures＇（SQS） approach of Zunger for the restoration of disorder around the observed site of alloys in the first few shells. The structural parameters have been predicted by minimizing the total energy in correspondence of unit cell volume. Our alloys established direct band gap at different concentrations that make their importance in optically active materials. Furthermore, density of states was discussed in terms of the contribution of Be and Mg s and chalcogen （S, Se, and Te） s and p states and observed charge density helped us to investigate the bonding nature. By taking into consideration of immense importance in optoelectronics of these materials, the complex dielectric function was calculated for incident photon energy in the range 0--15 eV.

关键词： BexMgl-xX (X = S Se Te) alloys zinc-blende (ZB) phase density functional theory (DFT),electronic and optical properties

Structural, electronic, and optical properties of ZnO_(1-x)Se_x alloys using first-principles calculations

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Chinese Physics B 2013年第8期22卷 581-588页

作者： Muhammad Rashid Fayyaz Hussain Muhammad Imran S A Ahmad n A noor M U Sohaib S M Alay-e-Abbas Department of Physics Simulation Laboratory the Islamia University of Bahawalpur63100 Pakistan Department of Physics University of the Punjab Quaid-e-Azam Campus54590 Lahore Pakistan Lahore Development Authority 54590 Lahore Pakistan Department of Physics GC University FaisalabadAllama Iqbal Road Faisalabad 38000 Pakistan

The structural, electronic, and optical properties of binary ZnO, ZnSe compounds, and their ternary ZnOl_xSex alloys are computed using the accurate full potential linearized augmented plane wave plus local orbital （FP-LAPW ＋ lo） method in the rocksalt （B 1） and zincblende （B3） crystallographic phases. The electronic band structures, fundamental energy band gaps, and densities of states for ZnO1_xSex are evaluated in the range 0 〈 x 〈 1 using Wu-Cohen （WC） generalized gradient approximation （GGA） for the exchange-correlation potential. Our calculated results of lattice parameters and bulk modulus reveal a nonlinear variation for pseudo-binary and their ternary alloys in both phases and show a considerable deviation from Vegard＇s law. It is observed that the predicted lattice parameter and bulk modulus are in good agreement with the available experimental and theoretical data. We establish that the composition dependence of band gap is semi-metallic in B1 phase, while a direct band gap is observed in B3 phase. The calculated density of states is described by taking into account the contribution of Zn 3d, O 2p, and Se 4s, and the optical properties are studied in terms of dielectric functions, refractive index, reflectivity, and energy loss function for the B3 phase and are compared with the available experimental data.

关键词： density functional theory alloys structural electronic optical properties

DFT investigation of half-metallic ferromagnetic rare earth based spinels MgHo_(2)Z_(4)(Z=S,Se)

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Journal of Rare Earths 2024年第1期42卷 121-128,I0005页

作者： Maiza Zanib Mumtaz Manzoor n.A.noor M.Waqas Iqbal Mazia Asghar H.H.Hegazy A.Laref Department of Physics Riphah International UniversityLahore CampusPakistan Research Centre for Advanced Materials Science King Khalid UniversityP.O.Box 9004AbhaSaudi Arabia Department of Physics Faculty of ScienceKing Khalid UniversityP.O.Box 9004AbhaSaudi Arabia Department of Physics and Astronomy College of ScienceKing Saud UniversityRiyadh11451Saudi Arabia

Half-metallic ferromagnetism,mechanical as well as thermoelectric properties for rare earth-based spinels MgHo_(2)Z_(4)(Z=S,Se)were investigated using density functional theory(DFT).Structural optimization was done with Perdew-Burke-Ehrenzorf(PBE)sol-generalized gradient approximation(GGA)to calculate the lattice constant of both spinels comparable to experimental *** addition,Born stability criteria and negative formation energy show that our studied spinels are also structurally and dynamically stable in the cubic *** ferromagnetic(FM)state stability,we also calculated the energy differences among FM,antiferromagnetic(AFM),and non-magnetic(nM)***,Curie temperatures of ferromagnetic phases were also *** used Trans-Blaha improved BeckeJohnson(TB-mBJ)potential functional for electronics as well as magnetic characteristics,which lead to the consistent explanation of half-metallic ferromagnetism,representing the whole band-occupancy in material with exact detail of density of states(DOS).The stable FM state was examined in spinels due to the exchange splitting of Ho cation consisting of p-d hybridizations compatible with the result achieved for electronics band structure and ***,spin magnetic moment was explained in terms of anion,cation,and sharing charge on studied *** addition,the calculated thermoelectric properties clearly show that operation range of these systems may be utilized by future experimental works for identifying the potential applications of these systems.

关键词： Ho-based spinels DFT simulations Mechanical parameters Electronic properties HM ferromagnetism Figure of merit

Optoelectronic Response of GeZn_(2)O_(4) through the Modified Becke-Johnson Potential

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Chinese Physics Letters 2012年第9期29卷 142-146页

作者： Iftikhar Ahmad B.Amin M.Maqbool S.Muhammad G.Murtaza S.Ali n.A.noor Department of Physics University of MalakandPakistan Materials Modeling Lab Department of PhysicsHazara University21300Pakistan Department of Physics and Astronomy Ball State UniversityIndiana47306-0505USA Department of Physics Islamia College UniversityPeshawarPakistan Department of Physics University of the PunjabQuaid-e-Azam Campus54590Pakistan

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 *** gap dependent optical parameters,like the dielectric constant,index of refraction,reflectivity and optical conductivity are calculated and *** 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 *** 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 ***,these phenomena can be explained by the fact that a signal must be transmitted as a wave packet rather than a monochromatic *** comprehensive theoretical study of the optoelectronic properties predicts that these materials can effectively be used in optical devices.

关键词： wave. dielectric approximation

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新型计算机系统对计算结构力学的影响

上海航天(中英文) 1988年第5期 47-48页

作者： Ahmed K·noor ,Sotya n·Atlui ,柳皆峻

在过去的20年中,计算机已有了爆炸性的增长,在下一个10年中,由于新型计算机结构和智能计算机的出现预期要增长得更快.下述的计算机硬/软件技术的进展会对结构力学产生很大的影响.

关键词：处理器浮点运算并行系统计算机系统

Aloe barbadensis Miller peptide/polypeptide fraction alleviates inflammation through inhibition of proinflammatory cytokines and mediators in vitro and in rats with Freund’s adjuvant-induced hind paw edema

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Asian Pacific Journal of Tropical Biomedicine 2019年第12期9卷 524-530页

作者： Spoorthy n.Babu Ayesha noor Centre for Bio Separation Technology Vellore Institute of TechnologyVelloreIndia

Objective:To evaluate the anti-inflammatory potential of peptide/polypeptide fraction of Aloe vera through in vitro and in vivo ***:The peptide/polypeptide fraction from Aloe vera was obtained through trichloroacetic acid *** anti-inflammatory property of the peptide/polypeptide fraction was tested by protein denaturation,membrane stabilization *** effect of the fraction on RAW 264.7 cell viability was examined by MTT *** nitric oxide level was determined through Griess ***-αand IL-6 levels were estimated using ELISA *** vivo studies were carried out in male Wistar rats through injection of Freund’s adjuvant in the hind *** edema was measured through the Vernier scale and levels of alanine aminotransferase,aspartate transaminase,TnF-α,IL-6,and secretory phospholipase A2 were estimated through their respective kits after fourteen days of *** Pad Prism6 was used for analyzing the ***:The peptide/polypeptide extract inhibited protein denaturation with an IC50 value of(218.9±15.6)μg/m L and stabilized the membrane of red blood cells with an IC50 value of(275.9±19.1)μg/m *** extract showed no changes in cell morphology or cytotoxicity up to the concentration of 20μg/mL in MTT *** peptide/polypeptide fraction markedly reduced the levels of proinflammatory markers and mediators in both in vitro and in vivo ***:The results indicate that the peptide/polypeptide fraction of Aloe vera has antiinflammatory property through inhibition of inflammatory markers and mediators responsible for nF-κB and mitogen-activated protein kinase pathways.

关键词： Aloe vera Peptide/Polypeptide Inflammation Proinflammatory cytokines

Rare earth elements in tropical surface water,soil and sediments of the Terengganu River Basin,Malaysia

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Journal of Rare Earths 2009年第6期27卷 1072-1078页

作者： Khawar Sultan noor Azhar Shazili Institute of Oceanography University Malaysia TerengganuMengabang Telipot21030 Kuala TerengganuTerengganuMalaysia

The 14 stable rare earth element(REE) concentrations and distribution patterns were investigated for surface waters(n=51),soils(n=52) and sediments(n=42) from the tropical Terengganu River basin,*** chondrite normalized REE patterns of soils developed on four geological units showed enrichment of LREE,a pronounced negative Eu,and depletion of HREE with an enrichment order granite>>metasedimentary>alluvium>*** REE patterns in sediments reflected the soil REE patterns with an ove...

关键词： rare earth elements river/lake water soil sediment Malaysia