Calculation Of Optical Properties Research Articles

First-principles calculations of electronic and optical properties of AgGa1-xTlxS2 alloys: Analyses and design for solar cell applications

The thallium substitution effect on structural, electronic, and optical properties of chalcopyrite-type material AgGaS2 is investigated via first-principles approaches. The computed band gap energy of pure AgGaS2 is about 2.59 ​eV using Tran-Blaha (TB)-modified Becke Johnson (mBJ) exchange potential, which is in good accord with experimental measurements. This band gap value was observed to decrease to be 1.91 ​eV, 1.61 ​eV, and 1.28 ​eV when Tl is substituted into Ga site, respectively, for 25%, 50%, and 75% concentrations. Besides, the AgTlS2 band gap was also calculated and found to be 0.61 ​eV. This investigation establishes that Tl substitution increases both hole and electron carrier mobility of the pure AgGaS2 compound. By analyzing the band alignment diagram, it was observed that the Tl substitution increases the valence band offset (VBO) and decreases the conduction band offset (CBO), which can lead to the improvement of open-circuit voltage VOC. Moreover, the optical analysis reveals that Tl substitution enhances the optical properties of AgGaS2 by reducing the transparency and improving the refractive index and the absorption in the visible light region. Based on obtained results, it is predicted that the band gap and the optical properties of the AgGaS2 chalcopyrite can be effectively tuned by Tl substitution over the Ga sites, making AgGa1-xTlxS2 alloys promising candidates for optoelectronic and photovoltaic applications.

Electronic and optical properties of ultra-small diameter armchair carbon and boron nitride nanotubes by PBE, TB-mBJ and YS-PBE0 functionals

We have investigated the electronic and optical properties of ultra-small (3,3), (4,4) and (5,5) armchair single walled nanotubes carbon (C-SWNTs) and boron nitride (BN-SWNTs) using three density functional methods of different categories, namely, PBE, TB-mBJ and hybrid functional YS-PBE0. A density functional theory (DFT) within the full-potential linearized augmented-plane wave (FP-LAPW) method, was used to study the structures, electronic and optical properties of these nanotubes. The calculation of optical properties has been performed under electric fields polarized both parallel and perpendicular with respect to the nanotube axis. The results show that the hybrid functional YS-PBE0 perform the best for calculations of band gap of BN-SWNTs (5.27–5.54 eV), while for C-SWNTs the PBE and TB-mBJ functionals obtain band gap range (0.16–0.28 eV) with smaller errors compared to experimental values and confirming the semiconducting behavior of the studied C-SWNTs. The dielectric function is anisotropic for all tubes and is larger in the parallel direction. The results show also that for C-SWNTs, the static refractive index is higher than those of BN-SWNTs and it has an inverse correlation with the C-SWNTs diameter. This proves that for optoelectronic applications, it is improve to use the BN-SWNTs doped than intrinsic.

Structural and optoelectronic properties of CsSnBr3 metal halide perovskite as promising materials toward novel-generation optoelectronics

In this study, first-principles density functional theory (DFT) calculations of the structural and optoelectronic properties of Sn-based inorganic metal halide perovskite CsSnBr3 are carried out and discussed in details. The Wu-Cohen (WC)-Generalized Gradient Approximation (GGA) based on the full-potential linearized augmented plane-wave (FPLAPW) method is used to optimize the geometry structure of unit cell and then find the accurate optoelectronic properties of CsSnBr3. Analysis of structural optimization results revealed that the lattice parameters (𝑎0 = 5.776 Å) and unit cell volume of CsSnBr3 are exactly consistent with the experiments reports. Based on the results of band structures and density of states, CsSnBr3 is found to be nonmagnetic semiconductor with suitable direct band gap of (Eg = 0.610 eV) along the R symmetry point. In addition, the calculations of optical properties of CsSnBr3, such as the real 𝜀1 (𝜔) and imaginary 𝜀2 (𝜔) parts of the dielectric function, 𝜀(𝜔), absorption coefficient 𝛼(𝜔), reflectivity 𝑅(𝜔) and refractive index 𝑛(𝜔), have been performed in the photonic energy range of (0.0 – 15.0 eV). Finally, the results attained in the present study, which include the stable crystal structure and the high accurate optoelectronic properties such as appropriate direct band gap and high absorption of visible radiation, confirm the possible utilization of CsSnBr3 materials in novel optoelectronics applications as photovoltaic solar cells, photosensors, photodetectors, photodiodes and other related optoelectronics devices

Theoretical investigation of structural, electronic, and optical properties of halide cubic perovskite CsPbBr3-xIx

The influence of the substitution of bromine (Br) with iodine (I) on electronic structure and optical characteristics of cubic perovskite CsPbBr3-xIx (x = 0.00, 0.12, 0.24, 0.33, 0.48, 1, 2 and 3) was investigated by the method of the full potential linearized augmented plane wave (FP-LAPW). This method was used within the framework of density functional theory as implemented in the wien2k code. In this work, Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA) was used for the treatment of exchange-correlation effects in calculations. The PBE-GGA and the modified Becke-Johnson potential combined to the GGA approximation (mBJ-GGA) were used for the calculations of electronic band structures and optical properties. The obtained results indicated that the lattice parameters of the studied compound increase as the substitution by iodine increases in the compound. These results are found to be in good agreement with those previously reported in literature. The effect of lattice constant on the bandgap has also been investigated. Moreover, the study of the electronic and optical properties of this halide perovskite CsPbBr3-xIx including the density of states, band structure, dielectric function, absorption coefficient was done. It was found that these compounds exhibit properties of semiconducting materials with a direct bandgap value ranging from 1.36 to 1.44 eV and absorption coefficients higher than 104 cm−1. These results clearly show that the CsPbBr3-xIx compounds can be used as promising candidates for solar cell and optoelectronic applications.

Comment on “The detailed calculations of optical properties of indium-doped CdO nanostructured films using Kramers-Kronig relations [Journal of Non-Crystalline Solids 552 (2021) 120,454] Lead borate glasses doped by lanthanum: Synthesis, physical, optical, and gamma photon shielding properties [Journal of Non-Crystalline Solids 527 (2020) 119,731] Effects of annealing on structural and optical properties of Ge20Se70Sn10 thin films for optoelectronic applications [Journal

In the literature, a widely spread equation to correlate between the optical (σoptic) and electrical (σelec) conductivities in the form of (σelec=2λσoptα). Unfortunately, the two sides of this equation have different dimensions; i.e. this equation is incorrect and the work by this equation must be stopped. Also, there is another equation suggested by Shankar and Joseph to correlate the electrical conductivity (σe) with the refractive index (n dimensionless), extinction- (k dimensionless) and absorption coefficient (α in m−1) in the form of σe=2kncα where c is the velocity of light and has m/s units. Unfortunately, the dimensions of the two sides of this equation are not the same and the work by this equation must also be stopped.

Calculation of Band Structures and Optical Properties in Zn3(Oh)2v2o7·2h2o by the Screened Exchange Density Functional

Calculation of Band Structures and Optical Properties in Zn3(Oh)2v2o7·2h2o by the Screened Exchange Density Functional

First Principles Calculations of Structural, Electronic and Optical Properties of Sn-Doped Zns

First Principles Calculations of Structural, Electronic and Optical Properties of Sn-Doped Zns

Density functional study of structural and optoelectronic properties of wurtzite MgxZn1−xTe ternary alloys

In the present density functional calculations of structural, electronic and optical properties of wurtzite MgxZn1−xTe ternary alloys, lattice constants (a0, c0) and band-gap (Eg) increases almost linearly with increasing Mg-concentration x. All the wurtzite specimens under this system are direct band-gap (Γ − Γ) semiconductors. Hexagonal symmetry results optical anisotropy in each specimen. Prominent peaks in the dielectric function spectra of the considered specimen are originated due to electronic excitations from Te-5p to Mg-4s, 3p and/or Zn-5s, 4p states. Nature of compositional variation of band-gap is opposite to the same of static dielectric constant, static refractive index and static reflectivity.

First-Principles Calculations of Structural, Energetic, Electronic, Optical, and Photocatalytic Properties of Batao2n Low-Index Surfaces

First-Principles Calculations of Structural, Energetic, Electronic, Optical, and Photocatalytic Properties of Batao2n Low-Index Surfaces

Insight into the exemplary structural, elastic, electronic and optical nature of GaBeCl3 and InBeCl3: a DFT study.

In the scheme of density functional theory (DFT), Structural, elastic, electronic, and optical properties calculations of GaBeCl3 and InBeCl3 are carried out using Tran–Blaha modified Becke–Johnson exchange potential approximation (TB-mBJ) installed in Wein2k software. Structurally the compounds of interest are found to be stable. Both compounds possess elastic stability, anisotropy, and ductility determined by the elastic studies. The electronic-band structure analysis shows the semiconductor nature of GaBeCl3 and InBeCl3 compounds with indirect band gaps of ∼3.08 eV for GaBeCl3 and ∼2.04 eV for InBeCl3 along with the symmetrical points from (X–Γ). The calculated total density of states (TDOS) and partial density of states (PDOS) of these compounds reveal that for the GaBeCl3 compound, the contribution of Ga (4p) and Cl (3p) orbital states in the valence, as well as the conduction band, is dominant. While for InBeCl3, the contribution of Cl (3p) states as well as In (5s) is large in the valence band and in that of Cl (3p-states) states in the conduction band. The type of chemical bonding is found to be ionic in both compounds. The optical properties i.e., the real (ε1(ω)) and imaginary (ε2(ω)) parts of dielectric function, refractive index n(ω), optical reflectivity R(ω), optical conductivity σ(ω), absorption coefficient α(ω), energy loss L(ω) and electron extinction coefficient k(ω) are also discussed in terms of optical spectra. It is reported that n(ω) and k(ω) exhibit the same characteristics as ε1(ω) and ε2(ω) respectively. Efficient application of these materials can be seen in semiconducting industries and many modern electronic devices.

Band-engineered Zn2TiO4 nanowires for hydrogen generation from water using visible light: A first-principles study

The electronic structure and optical properties of inverse-spinel Zn2TiO4 nanowires and bulk material were investigated for hydrogen generation from water by visible-light photocatalysis using first-principles density calculations. In our theoretical studies, the bandgap of the Zn2TiO4 nanowires was much smaller than that of the bulk material. New intermediate states appeared in the mid-bandgap as a result of Zn and Ti atoms on the surface of ZnO-terminated and ZnTiO-terminated nanowires. These deep-level states could become recombination centers for photogenerated electron–hole pairs, indicating that these two types of nanowires would no longer meet the requirements for photocatalytic water splitting. In contrast, the electronic states arising from oxygen elements on the surface of the TiO-terminated nanowires resulted in an upward movement of the edge of the valence band, whereas the surface electronic states made no difference to the edge of the conduction band. Moreover, the optical property calculations showed that the optical absorption edge of the nanowire would be red-shifted. These calculations revealed that inverse-spinel Zn2TiO4 nanowires were appropriate for visible-light photocatalytic water splitting reactions.

A comprehensive computational investigations on the physical properties of TiXSb (X: Ru, Pt) half‐Heusler alloys and Ti2RuPtSb2 double half‐Heusler

AbstractIn this paper, we have investigated the structural, elastic, optoelectronic and thermoelectric properties of the new half‐Heusler alloys TiXSb (X: Ru, Pt) and Ti2RuPtSb2 double half‐Heusler compound, using the full‐potential linearized augmented plane wave method. Different approximations for the exchange‐correlation functional were performed as generalized gradient approximation + Hubbard potential (GGA + U) and its combination with the modified Becke–Johnson potential. The negative values of the calculated formation energy indicate that these compounds are energetically stable. Both half Heusler alloys are half‐metallic ferromagnetic materials and exhibit an integer magnetic moment of Mt = 1.00 μB. While, the Ti2RuPtSb2 is a direct semiconductor at center symmetry. The calculations of optical properties revealed that Ti2RuPtSb2 compound exhibits an excellent optical efficiency. The thermoelectric properties such as the Seebeck coefficient (S); electronic thermal conductivity (κe/τ), power factor (PF), and figure of merit (ZT) have been studied and discussed in detail. Consequently, the investigated compounds were identified as candidate materials for high technological applications.

Encapsulation of atomic hydrogen and gaseous molecules in single-walled boron–nitrogen nanotubes: A computational study

First-principles calculations on the encapsulation of atomic hydrogen and some diatomic and triatomic molecules in single-walled (5,5) and (9,0) boron–nitrogen nanotubes are performed. The encapsulation procedure is addressed through the analysis of the electronic and structural properties, such as the adsorption energy, band-structures and density of states. Charge-density transfer, current vs bias voltage and optical properties calculations are also performed. NO2 encapsulation produces the most stable system among all the agents considered in the present study. While the encapsulated H, O2, NO and NO2 systems show metallic character, H2, N2, CO and CO2 encapsulation demonstrate a semiconducting nature. The dielectric function and conductance depend on the helicity of the nanotube and also on the nature of the encapsulated agent.

First-principles calculations of elastic and optical properties of Aluminum Nitride (AlN) in cubic and hexagonal phase

Investigation of elastic and optical properties of AlN in rock salt, zinc blende, and wurtzite phase is done under the framework of Density Functional Theory (DFT) with modified Becke Johnson Generalised Gradient Approximation (mBJ-GGA) as exchange-correlation functional. Elastic properties conclude the bonding nature of the AlN in the rock salt phase is covalent and stiffest, while the bonding nature in the zinc blende and wurtzite phase is found to be ionic and less stiff. The ratio of bulk modulus to shear modulus indicates AlN is brittle in all three phases. The calculated Debye temperature in all three phases is in good agreement with the available theoretical and experimental works. The optical properties calculation shows the AlN is transparent in the low energy range and it has the metallic behavior in the energy range 7.5eV to 10 eV. At the same time, the compound loses its transparency at the high energy range. Our calculated value of the refractive index of AlN in the rock salt, zinc blende, and wurtzite phases is in good agreement with the available experimental and theoretical works.

First Principles Calculations of Electronic and Optical Properties of KSbO3 under Pressure

First Principles Calculations of Electronic and Optical Properties of KSbO3 under Pressure

First-principles study of the structural and optoelectronic properties of ANbO3 (A = Na, K and Rb) in four crystal phases

In the present work structural and optoelectronic properties of alkali niobates ANbO3 (A = Na, K and Rb) are investigated in different crystal structures e.g. cubic, tetragonal, orthorhombic and rhombohedral using generalized gradient approximation (GGA), GGA with Hubbard potential (GGA + U) and modified Becke-Johnson (mBJ) approach. Structural properties show that ferroelectric rhombohedral crystal structure is the most stable structure of these compounds. The anti-ferroelectric and paraelectric are their higher energy crystal structures. The obtained results of the electronic band gaps show that mBJ is the appropriate exchange-correlation approximation for the calculations of electronic and optical properties of these niobates. They are indirect band gap semiconductors, except the ferroelectric rhombohedral and antiferroelectric orthorhombic NaNbO3. The valence band is predominantly contributed by O 2p orbitals and conduction band is made of Nb 4d orbitals. Real and imaginary parts of dielectric function and other optical parameters such as energy loss function, sum rule and refractive index are also investigated.

First-principles calculations of electronic and optical properties of orthorhombic Bi2Se3 nano thin film

This study explored the electronic and optical properties of nano-thin film orthorhombic bismuth selenide (Bi2Se3) using first-principles approach. The thin films were modelled in the [001] direction using slab geometry supercell with vacuum along z-direction so that periodic images and slab can be managed independently. We obtained band gap of 0.730 eV, 0.566 eV and 0.690 eV for 1, 2 and 3 slabs respectively. It shows dependence of band structure to the thickness of the films. The reduced band gap in Bi2Se3 films is due to the effect of quantum confinement. The electron contributions were increased as the thickness of the thin film increased. We also found that the thickness of Bi2Se3 thin film influences its optical properties. Higher thickness provides higher static dielectric function, refractive index, extinction coefficient, absorption coefficient and loss function. This study demonstrates Bi2Se3 thin film has good optical properties that are useful for optoelectronic applications.

Investigation of polar crystalline materials containing hydrochlorothiazide: electron density distribution and optical properties

The polar hydrochlorothiazide polymorph (I) (systematic name: 6-chloro-1,1-dioxo-3,4-dihydro-2H-1,2,4-benzothiadiazine-7-sulfonamide, C7H8ClN3O4S2) and, recently designed by us, the polar 2-aminopyridine hydrochlorothiazide water <1/1/1> (C7H8ClN3O4S2·C5H6N2·H2O), (II), have been investigated. The crystal structures of both materials were determined using the single-crystal X-ray diffraction technique. The intermolecular interactions in (I) and (II) were studied in detail via topological electron-density analysis. The obtained results showed hydrogen bonds with a character intermediate between closed-shell and shared-shell in both crystal structures. The most important hydrogen bonds in (I) are formed between sulfonamide groups, whereas in (II), water molecules play a crucial role as they interconnect 2-aminopyridine and hydrochlorothiazide molecules. Calculations of the optical properties revealed that both materials exhibit large linear birefringence, twice that of calcite. The theoretically predicted second harmonic generation efficiency is four times and five times larger than that of KH2PO4 for (I) and (II), respectively. The information gathered on intermolecular interactions and structure–property correlations was used to identify the best strategies for the future design of new functional materials of this kind.

Pressure induced structural, electronic and optical properties of wurtzite beryllium monoxide (w-BeO) from first-principle calculations

All-electron density functional calculations of structural, electronic and optical properties of wutrzite beryllium oxide (w-BeO) are carried out at different applied hydrostatic pressure. Calculated lattice constants decrease (a, c), while bulk modulus increases with increasing pressure. Direct fundamental band-gap (Eg) of w-BeO increases with increasing pressure and vice versa and the variation provides first and second order pressure coefficient of band-gap. The calculated volume deformation potential of band-gap of w-BeO is −11.5972 eV. Optical properties of w-BeO at zero and high pressures have been studied in terms of dielectric function ε(ω) and related ancillary optical parameters. Each optical parameter is marginally anisotropic. Calculated components of refractive index at each pressure signify uniaxial characteristics of the w-BeO. Calculated components of static dielectric constant, refractive index and reflectivity decreases, while critical point energy in the spectra of each component of ε2(ω), k(ω), σ(ω) and α(ω) increases with increasing pressure and vice versa. Calculated optical energy-gap (Eopt) of w-BeO increases like Eg with increasing pressure and vice versa. The transmission cutoff energy (ECutoff) is shifted towards the higher energy region with increasing pressure.

First principle calculation of electronic, optical and magnetic properties of Zn1−xFexSe compound

By employing the first principles method within the generalized gradient approximation for the exchange and correlation potential, the electronic, optical and magnetic properties of pure and Fe-doped zinc-blende ZnSe are investigated. According to the obtained band structure, density of state and optical spectrum the electronic origin of the maxima in the optical spectrum has been observed. The optical spectrum peak is generated mainly from the charge transfer between the Se(4[Formula: see text] and Zn(3[Formula: see text] states. Our results reveal that the strong spin polarization of the 3[Formula: see text] states of the Fe atoms is the origin of antiferromagnetism in Zn[Formula: see text]Fe[Formula: see text]Se. A decrease in the concentration of iron atoms in the supercell does not affect the stability of the AFM phase.