Publications by authors named "Khandaker Monower Hossain"

The effects of alkaline-earth metals on electronic, optical, thermodynamic, and physical properties of ferromagnetic AVO (A = Ba, Sr, Ca, and Mg) have been investigated by first-principles calculations within the GGA+ formalism based on density functional theory. The optimized structural parameters are in good agreement with the available experimental results that evaluate the reliability of our calculations. The cell and mechanical stability is discussed using the formation energy and Born stability criteria, respectively. The mechanical behaviors of AVO are discussed on the basis of the results of elastic constants, elastic moduli, Peierls stress, and Vickers hardness. The nature of the ductile-brittle transition of AVO compounds was confirmed by the values of Pugh's ratio, Poisson's ratio, and Cauchy pressure. The electronic band structures, as well as density of states, reveal the half-metallic behavior of BaVO and SrVO. However, CaVO and MgVO exhibit spin-gapless and magnetic semiconductor characteristics, respectively. The microscopic origin of the transition from the half-metallic to semiconductor nature of AVO is rationalized using electronic properties. The presence of covalent, ionic, and metallic bonds in AVO compounds is found by the analysis of bonding properties. The single-band nature of half-metallic AVO is seen by observing hole-like Fermi surfaces in this study. Furthermore, the various thermodynamic and optical properties are calculated and analyzed. The refractive index suggests that AVO could be a potential candidate for applications to high-density optical data storage devices.

The current study diligently analyzes the physical characteristics of halide perovskites AGeF (A = K, Rb) under hydrostatic pressure using density functional theory. The goal of this research is to reduce the electronic band gap of AGeF (A = K, Rb) under pressure in order to improve the optical characteristics and assess the compounds' suitability for optoelectronic applications. The structural parameters exhibit a high degree of precision, which correlates well with previously published work. In addition, the bond length and lattice parameters decrease significantly leading to a stronger interaction between atoms. The bonding between K(Rb)-F and Ge-F reveal ionic and covalent nature, respectively, and the bonds become stronger under pressure. The application of hydrostatic pressure demonstrates remarkable changes in the optical absorption and conductivity. The band gap becomes lower with the increment of pressure, resulting in better conductivity. The optical functions also predict that the studied materials might be used in a variety of optoelectronic devices operating in the visible and ultraviolet spectrum. Interestingly, the compounds become more suitable to be used in optoelectronic applications under pressure. Moreover, the external pressure has profound dominance on the mechanical behavior of the titled perovskites, which make them more ductile and anisotropic.

Density functional theory is utilized to explore the effects of hydrostatic pressure on the structural, electrical, optical, and mechanical properties of cubic halide perovskite KCaCl throughout this study. The interatomic distance is decreased due to the pressure effect, which dramatically lowers the lattice constant and unit cell volume of this perovskite. Under pressure, the electronic band gap shrinks from the ultra-violet to visible region, making it easier to move electrons from the valence band to the conduction band, which improves optoelectronic device efficiency. Furthermore, the band gap nature is switched from indirect to direct around 40 GPa pressure, which is more suitable for a material to be exploited in optoelectronic applications. The use of KCaCl in microelectronics, integrated circuits, QLED, OLED, solar cells, waveguides, solar heat reduction materials, and surgical instruments has been suggested through deep optical analysis. The use of external hydrostatic pressure has a considerable impact on the mechanical properties of this material, making it more ductile and anisotropic.

A novel distorted perovskite-type (KSr)(NaCaBi)O was prepared by a hydrothermal method using the starting materials NaBiO·HO, Sr(OH)·8HO, Ca(OH), and KOH. Single-crystal X-ray diffraction of the novel compound revealed a GdFeO-related structure belonging to the monoclinic system of the space group with the following cell parameters: = 11.8927 (17) Å, = 11.8962 (15) Å, = 8.4002 (10) Å, and β = 90.116 (9)°. The final -factors were obtained as = 0.0354 and w = 0.0880 (using all the data). K and Sr ions were distributed at four types of A-sites. On the other hand, four Bi-sites (Bi1, Bi2, Bi3, and Bi4) were occupied by four Ca ions (Ca1, Ca2, Ca3, and Ca4), and the first three B-sites were occupied predominantly by Bi with Na ions. The forth B-site was occupied predominantly by the Ca ion with Bi ions. Two types of B-sites, thus forming tilted distorted (Na/Ca/Bi)O and (Bi/Ca)O octahedra, have an ordering of 3:1 represented as (K/Sr)(Na/Ca/Bi)(Bi/Ca)O. The distorted (Na/Ca/Bi)O and (Ca/Bi)O octahedra formed a perovskite-type network by corner sharing with features closely matching those of a GdFeO-type structure. The novel compound is the first example of a perovskite-type bismuth oxide containing only Bi in a system without a Ba atom and has a unique ordering (3:1) of the B site. The compound showed photocatalytic activity for phenol degradation under visible light irradiation.

In this article, we perform density functional theory calculation to investigate the electronic and optical properties of newly reported In Se compound using CAmbridge Serial Total Energy Package (CASTEP). Structural parameters obtained from the calculations agree well with the available experimental data, indicating their stability. In the band structure of In Se ( = 0, 0.11, and, 0.22), the Fermi level ( ) crossed over several bands in the conduction bands, which is an indication of the n-type metal-like behavior of In Se compounds. On the other hand, the band structure of In Se ( = 1/3) exhibits semiconducting nature with a band gap of ∼0.2 eV. A strong hybridization among Se 4s, Se 4p and In 5s, In 5p orbitals for InSe and that between Se 4p and In 5p orbitals were seen for β-InSe compound. The dispersion of In 5s, In 5p and Se 4s, Se 4p orbitals is responsible for the electrical conductivity of InSe that is confirmed from DOS calculations as well. Moreover, the bonding natures of In Se materials have been discussed based on the electronic charge density map. Electron-like Fermi surface in InSe ensures the single-band nature of the compound. The efficiency of the In Se/p-Si heterojunction solar cells has been calculated by Solar Cell Capacitance Simulator (SCAPS)-1D software using experimental data of In Se thin films. The effect of various physical parameters on the photovoltaic performance of In Se/p-Si solar cells has been investigated to obtain the highest efficiency of the solar cells. The optimized power conversion efficiency of the solar cell is found to be 22.63% with = 0.703 V, = 38.53 mA/cm, and FF = 83.48%. These entire theoretical predictions indicate the promising applications of In Se two-dimensional compound to harness solar energy in near future.