Exploring the electronic structure and optical properties of new inorganic luminescent materials Ba(Si,Al)5(O,N)8 compounds for lightemitting diodes devices

Sikander Azam,Saleem Ayaz Khan,Jan Minar,Souraya Goumri-Said 한국물리학회 2015 Current Applied Physics Vol.15 No.10

Due to growing demand on discovering new materials for light-emitting diodes devices, many efforts were made to discover and characterize new inorganic materials such as phosphors. Using the full potential method within density functional theory the electronic and optical properties of BaAl2Si3O4N4 and BaAlSi4O3N5 semiconductors have been investigated. The electronic structure and the optical properties of these phosphors were calculated through a reliable approach of modified Beck-Johnson (mBJ) approach. We found that BaAl2Si3O4N4 and BaAlSi4O3N5 have wide direct band gaps positioned at G about 5.846 and 4.96 eV respectively. The optical properties, namely the dielectric function, optical reflectivity, refractive index and electron energy loss, are reported for radiation up to 15 eV. Our study suggests that BaAl2Si3O4N4 and BaAlSi4O3N5 could be promising materials for applications in the LEDs devices and optoelectronics areas of research.

A first-principles theoretical investigation of the structural, electronic and magnetic properties of cubic thorium carbonitrides ThCxN(1-x)

Muhammad Siddique,Amin Ur Rahman,Azmat Iqbal,Sikander Azam 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.5

Besides promising implications as fertile nuclear materials, thorium carbonitrides are of great interestowing to their peculiar physical and chemical properties, such as high density, high melting point, goodthermal conductivity. This paper reports first-principles simulation results on the structural, electronicand magnetic properties of cubic thorium carbonitrides ThCxN(1-x) (X ¼ 0.03125, 0.0625, 0.09375, 0.125,0.15625) employing formalism of density-functional-theory. For the simulation of physical properties, weincorporated full-potential linearized augmented plane-wave (FPLAPW) method while the exchangecorrelationpotential terms in Kohn-Sham Equation (KSE) are treated within Generalized-Gradient-Approximation (GGA) in conjunction with Perdew-Bruke-Ernzerhof (PBE) correction. The structuralparameters were calculated by fitting total energy into the Murnaghan's equation of state. The latticeconstants, bulk moduli, total energy, electronic band structure and spin magnetic moments of thecompounds show dependence on the C/N concentration ratio. The electronic and magnetic propertieshave revealed non-magnetic but metallic character of the compounds. The main contribution to densityof states at the Fermi level stems from the comparable spectral intensity of Th (6dþ5f) and (CþN) 2pstates. In comparison with spin magnetic moments of ThSb and ThBi calculated earlier with LDAþUapproach, we observed an enhancement in the spin magnetic moments after carbon-doping into ThNmonopnictide.

Mechanical and thermodynamic stability, structural, electronics and magnetic properties of new ternary thorium-phosphide silicides ThSi_xP_1-x: First-principles investigation and prospects for clean nuclear energy applications

Siddique, Muhammad,Iqbal, Azmat,Rahman, Amin Ur,Azam, Sikander,Zada, Zeshan,Talat, Nazia Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.2

Thorium compounds have attracted immense scientific and technological attention with regard to both fundamental and practical implications, owing to unique chemical and physical properties like high melting point, high density and thermal conductivity. Hereby, we investigate the mechanical and thermodynamic stability and report on the structural, electronic and magnetic properties of new silicon-doped cubic ternary thorium phosphides ThSi_xP_1-x (x = 0, 0.25, 0.5, 0.75 and 1). The first-principles density functional theory procedure was adopted within full-potential linearized augmented plane wave (FP-LAPW) method. The exchange and correlation potential terms were treated within Generalized-Gradient-Approximation functional modified by Perdew-Burke-Ernzerrhof parameterizations. The proposed compounds showed mechanical and thermodynamic stable structure and hence can be synthesized experimentally. The calculated lattice parameters, bulk modulus, total energy, density of states, electronic band structure and spin magnetic moments of the compounds revealed considerable correlation to the Si substitution for P and the relative Si/P doping concentration. The electronic and magnetic properties of the doped compounds rendered them non-magnetic but metallic in nature. The main orbital contribution to the Fermi level arises from the hybridization of Th(6d+5f) and (Si+P)3p states. Reported results may have potential implications with regard to both fundamental point of view and technological prospects such as fuel materials for clean nuclear energy.

Cloning and Functional Characterization of Endo-β-1,4-Glucanase Gene from Metagenomic Library of Vermicompost

Muhammad Yasir,Haji Khan,Syed Sikander Azam,Amar Telke,Seon Won Kim,Young Ryun Chung 한국미생물학회 2013 The journal of microbiology Vol.51 No.3

In the vermicomposting of paper mill sludge, the activity of earthworms is very dependent on dietetic polysaccharides including cellulose as energy sources. Most of these polymers are degraded by the host microbiota and considered potentially important source for cellulolytic enzymes. In the present study, a metagenomic library was constructed from vermicompost (VC) prepared with paper mill sludge and dairy sludge (fresh sludge, FS) and functionally screened for cellulolytic activities. Eighteen cellulase expressing clones were isolated from about 89,000 fosmid clones libraries. A short fragment library was constructed from the most active positive clone (cMGL504) and one open reading frame (ORF) of 1,092 bp encoding an endo-β-1,4-glucanase was indentified which showed 88% similarity with Cellvibrio mixtus cellulase A gene. The endo-β-1,4-glucanase cmgl504 gene was overexpressed in Escherichia coli. The purified recombinant cmgl504 cellulase displayed activities at a broad range of temperature (25–55°C) and pH (5.5–8.5). The enzyme degraded carboxymethyl cellulose (CMC) with 15.4 U, while having low activity against avicel. No detectable activity was found for xylan and laminarin. The enzyme activity was stimulated by potassium chloride. The deduced protein and three-dimensional structure of metagenomederived cellulase cmgl504 possessed all features, including general architecture, signature motifs, and N-terminal signal peptide, followed by the catalytic domain of cellulase belonging to glycosyl hydrolase family 5 (GHF5). The cellulases cloned in this work may play important roles in the degradation of celluloses in vermicomposting process and could be exploited for industrial application in future.

Investigation of electronic and optical properties of the ternary chalcogenides for optoelectronic applications: A TB-mBJ DFT study

Goumri-Said Souraya,Shah Mazhar Ali,Azam Sikander,Irfan Muhammad,Kanoun Mohammed Benali 한국물리학회 2023 Current Applied Physics Vol.49 No.-

Ternary selenide chalcogenide Tl3AsSe3 compound was identified as one of the most promising novel materials and potentially appropriate for multifunction applications. Current computational study is focused on computation of optical properties of Tl3AsX3 (X = S and Se) system where Modified Becke Johnson (mBJ) approximation is employed. The calculations of band structure revealed that both materials were indirect bandgap semiconducting materials with bandgap 1.5 eV and 1.9 eV respectively. The valence band maxima are mainly created because of Tl/As/S/Se(s/p/p/p) orbitals and conduction band is formed thanks to hybridizations of Tl/ As/S/Se(p) orbitals. The optical properties including complex dielectric function, reflectivity, energy loss function, refractive index, and real optical conductivity also calculated by using first-principles calculations. Our investigations explained that the two materials sustain their positive value of the refractive index and thus is the non-negative index of refractions, so these materials are active candidates for optoelectronic applications.

First-Principles Description of the Different Phases in the Li$_{2}$NH Compound: Electronic Structure and Optical Properties

Madiha Makhdoom,Muhammad Imran Jamil,Sikander Azam,Muhammad Irfan,Zeesham Abbas,Banat Gul,Saleem Ayaz Khan,Xiaotian Wang 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.74 No.12

A hydrogen storage material can also be used as a potential and effective solid reducing agent in addition to its applications as an important energy carrier. The density function theory has been used to find the structural and optoelectronic properties of the Li$_{2}$NH compound. The exchange-correlation functional based GGA (generalized gradient approximation) is applied for calculating structural and optoelectronic properties. The expression for the formation is used to identify the stability, which is further confirmed by calculating the structural properties of Li$_{2}$NH. The calculations of the band structure show that a direct band gap is present between the occupied Li and N orbitals. A deep analysis of the optical properties was performed under incident photon radiation at energies up to 14 eV. Our calculated refractive index $n$(0) and the static part of the dielectric constant $\varepsilon_{2}$(0) are analogous to the experimental and other reported theoretical value.

Proteome‑wide subtractive approach to prioritize a hypothetical protein of XDR‑Mycobacterium tuberculosis as potential drug target

Reaz Uddin,Quratulain Nehal Siddiqui,Muhammad Sufian,Syed Sikander Azam,Abdul Wadood 한국유전학회 2019 Genes & Genomics Vol.41 No.11

Background Among the resistant isolates of MTB, multidrug resistant tuberculosis (MDR-TB) and extensively drug resistant tuberculosis (XDR-TB) have been the areas of growing concern. The genomic analysis showed that the respective genomic pool of the XDR-MTB proteome contains more than 30% of the hypothetical proteins for which no functions have been annotated yet. This class of proteins presumably have their own importance to complete genome and proteome information. The bioinformatics advancements have helped to annotate those hypothetical proteins by using various computational tools and have potential to classify them functionally. Objective The objective of this study was to propose a new and unique drug target against the deadly Mycobacterium tuberculosis using Bioinformatics approaches to characterize the hypothetical proteins. Results We stepwise reduced the hypothetical proteins (total number: 1256) out of the complete proteome to only 26 essential hypothetical proteins. Out of those 26 proteins, the protein WP_003401246.1 was computationally characterized as the druggable target. Conclusion The study proposed a hypothetical protein from complete proteome of the XDR-MTB as a new drug target against which new drug candidates can be proposed. Hence, the study opens up the new avenues in the areas of drug discovery against deadly M. tuberculosis.

Nonlocal dynamic modeling of mass sensors consisting of graphene sheets based on strain gradient theory

Mehrez, Sadok,Karati, Saeed Ali,DolatAbadi, Parnia Taheri,Shah, S.N.R.,Azam, Sikander,Khorami, Majid,Assilzadeh, Hamid Techno-Press 2020 Advances in nano research Vol.9 No.4

The following composition establishes a nonlocal strain gradient plate model that is essentially related to mass sensors laying on Winkler-Pasternak medium for the vibrational analysis from graphene sheets. To achieve a seemingly accurate study of graphene sheets, the posited theorem actually accommodates two parameters of scale in relation to the gradient of the strain as well as non-local results. Model graphene sheets are known to have double variant shear deformation plate theory without factors from shear correction. By using the principle of Hamilton, to acquire the governing equations of a non-local strain gradient graphene layer on an elastic substrate, Galerkin's method is therefore used to explicate the equations that govern various partition conditions. The influence of diverse factors like the magnetic field as well as the elastic foundation on graphene sheet's vibration characteristics, the number of nanoparticles, nonlocal parameter, nanoparticle mass as well as the length scale parameter had been evaluated.

Theoretical investigation of electronic structure and optical response in relation to the transport properties of Ga1-xInxN (x = 0, 0.25, 0.50, 0.75)

Fahad Ali Shah,Saleem Ayaz Khan,Suneela Arif,Sikander Azam,R. Khenata,S. Bin Omran 한국물리학회 2015 Current Applied Physics Vol.15 No.5

The state-of-the-art all-electron FLPAW method and the BoltzTrap software package based on semiclassical theory were adopted to explore the electronic structure and the optical and thermoelectric properties of Ga1-xInxN. Ga1-xInxN is predicted to be a direct band gap material for all values of x. Moreover, the band gap varies between 2.99 eV and 1.95 eV as x changes. Optical parameters such as the dielectric constant, absorption coefficient, reflectivity and refractive index are calculated and discussed in detail. The doping of In plays an important role in the modulation of the optical constants. The static dielectric constant ε (0) of Ga1-xInxN was calculated as 3.95, 3.99, 3.99 and 4.03 at x = 0.00, 0.25, 0.50 and 0.75, respectively. The static refractive index is 2.0 for pure Ga1-xInxN at x = 0.00. The thermal properties varied greatly as x fluctuated. The ternary alloy has large values for the Seebeck coefficient and figure of merit at high temperatures and is thus suitable for thermoelectric applications. Pure Ga1-xInxN at x = 0 exhibited ZT = 0.80 at room temperature, and at higher temperatures, the thermal conductivity decreased with increased In doping.