Calculation Of Optical Properties Research Articles

FROG: Exploiting all-atom molecular dynamics trajectories to calculate linear and non-linear optical responses of molecular liquids within Dalton's QM/MM polarizable embedding scheme.

Quantum mechanical/molecular mechanics (QM/MM) methods are interesting to model the impact of a complex environment on the spectroscopic properties of a molecule. In this context, a FROm molecular dynamics to second harmonic Generation (FROG) code is a tool to exploit molecular dynamics trajectories to perform QM/MM calculations of molecular optical properties. FROG stands for "FROm molecular dynamics to second harmonic Generation" since it was developed for the calculations of hyperpolarizabilities. These are relevant to model non-linear optical intensities and compare them with those obtained from second harmonic scattering or second harmonic generation experiments. FROG's specificity is that it is designed to study simple molecular liquids, including solvents or mixtures, from the bulk to the surface. For the QM/MM calculations, FROG relies on the Dalton package: its electronic-structure models, response theory, and polarizable embedding schemes. FROG helps with the global workflow needed to deal with numerous QM/MM calculations: it permits the user to separate the system into QM and MM fragments, to write Dalton's inputs, to manage the submission of QM/MM calculations, to check whether Dalton's calculation finished successfully, and finally to perform averages on relevant QM observables. All molecules within the simulation box and several time steps are tackled within the same workflow. The platform is written in Python and installed as a package. Intermediate data such as local electric fields or individual molecular properties are accessible to the users in the form of Python object arrays. The resulting data are easily extracted, analyzed, and visualized using Python scripts that are provided in tutorials.

Effect of doped heteroatom on monolayer SnSe2 adsorption of Na

Based on the first principles, we have calculated the influence of B, Br, and N atom doping on the adsorption properties and optoelectronic properties of monolayer SnSe2 adsorbed Na. The calculations show that vacancy is the most favorable adsorption site for the Na atom. Among the three doping systems, the B-doped system has the best adsorption energy and height and Na’s adsorption capacity. After the adsorption of the Na atom by intrinsic SnSe2, the system behaves from a semiconductor to a metal nature. Doping Br atom increases the adsorption system’s Fermi energy level, the conduction band’s overall energy increases and the electrical conductivity is enhanced. Doping B and N atoms change the adsorption system from metallic to p-type semiconductor properties. The system’s adsorption performance, electrical conductivity, and energy band tunability are improved. Due to the electrostatic repulsion between Na atoms, the adsorption energy of the system shows an increasing trend with the increase in the number of adsorbed Na atoms on the surface. The maximum specific capacity of the surface of the doped system is 373 mAhg−1, and the system has high storage capacity. Optical property calculations show that the static refractive index of the Br-doped adsorption system is maximum. The static refractive index of the doped adsorption system is minimal. Doping makes the system’s energy loss smaller, complex conductivity decreases, intermolecular interactions decrease, and the adsorption system becomes more stable.

First-principles calculations of structural, elastic, electronic, magnetic, optical, thermoelectric, and dynamic properties of CoCrTe half-Heusler compound

First-principles calculations of structural, elastic, electronic, magnetic, optical, thermoelectric, and dynamic properties of CoCrTe half-Heusler compound

Towards the Analytical Generalization of the Transcendental Energy Equation, Group Velocity, and Effective Mass in One-Dimensional Periodic Potential Wells with a Computational Application to Common Coupled Potentials

The analytical generalization for N periodic potential wells coupled to a probe rectangular-like potential and a zero potential is extremely important in the study of one-dimensional periodic potentials in solid state physics, e.g., in the calculation of transport, optical, and magnetic properties. These findings raise the possibility of calculating equations for the generalization of N arbitrary potentials related to any potential V(x) using special functions as a solution. In this work, a novel analytical generalization of the transcendental energy equation, group velocity, and effective mass for N-coupled potentials to a probe one-dimensional potential V=V(x) was proposed. Initially, two well-known linear periodic potentials V=V(x) were employed to obtain analytical solutions for rectangular-like and Dirac-delta potentials. Python libraries were used to easily represent the equations for one or two rectangular-like potentials coupled with an arbitrary potential, highlighting the transcendental energy, group velocity, and effective mass. The results showed that the group velocity behavior changed its orientation due to the sign of the potential, whereas the width of the potential V(x) strongly influenced the group velocity behavior. The effective mass was also modified by the potential shapes, and their combinations, both effective mass and group velocity, exhibited similar physical behaviors to those found in ordinary rectangular-like potentials.

Theoretical and experimental determination of the confocal function of OCT systems for accurate calculation of sample optical properties

The attenuation coefficient of biological tissue could serve as an indicator of structural and functional changes related to the onset or progression of disease. Optical coherence tomography (OCT) provides cross sectional images of tissue up to a depth of a few millimeters, based on the local backscatter properties. The OCT intensity also depends on the confocal function, which needs to be characterised to determine correctly the exponential decay of the intensity based on Lambert-Beer. We present a model for the confocal function in scattering media based on the illumination with a Gaussian beam and the power transfer into a single mode fibre (SMF) of the backscattered light for an incoherently back scattered Gaussian beam using the Huygens-Fresnel principle and compare that model with the reflection from a mirror. We find that, contrary to previous literature, the confocal functions characterised by the Rayleigh range in the two models are identical. Extensive OCT focus series measurements on a mirror, Spectralon and Intralipid dilutions confirm our model, and show that for highly scattering samples the confocal function characterised by the Rayleigh range becomes depth dependent. From the diluted Intralipid measurements the attenuation coefficients are extracted using a singly scatter model that includes the previously established confocal function. The extracted attenuation coefficients were in good agreement for weakly scattering samples (μ s < 2 mm−1).

Flexibility potential of Cs2BX6 (B = Hf, Sn, Pt, Zr, Ti; X = I, Br, Cl) with application in photovoltaic devices and radiation detectors

As interest in double perovskites is growing, especially in applications like photovoltaic devices, understanding their mechanical properties is vital for device durability. Despite extensive exploration of structure and optical properties, research on mechanical aspects is limited. This article builds a vacancy-ordered double perovskite model, employing first-principles calculations to analyze mechanical, bonding, electronic, and optical properties. Results show Cs2HfI6, Cs2SnBr6, Cs2SnI6, and Cs2PtBr6 have Young's moduli below 13 GPa, indicating flexibility. Geometric parameters explain flexibility variations with the changes of B and X site composition. Bonding characteristic exploration reveals the influence of B and X site electronegativity on mechanical strength. Cs2SnBr6 and Cs2PtBr6 are suitable for solar cells, while Cs2HfI6 and Cs2TiCl6 show potential for semi-transparent solar cells. Optical property calculations highlight the high light absorption coefficients of up to 3.5×105 cm−1 for Cs2HfI6 and Cs2TiCl6. Solar cell simulation shows Cs2PtBr6 achieves 22.4% of conversion efficiency. Cs2ZrCl6 holds promise for ionizing radiation detection with its 3.68 eV bandgap and high absorption coefficient. Vacancy-ordered double perovskites offer superior flexibility, providing valuable insights for designing stable and flexible devices. This understanding enhances the development of functional devices based on these perovskites, especially for applications requiring high stability and flexibility.

Influence of different terminations on the surface properties of MB2: first principles study

Metal diborides MB2 (M = Zr, V, Ta, Nb) are widely used in many optoelectronic devices. Investigation into their surface stability and morphology is the first and essential step in exploring their properties. In the present work, the periodic density functional theory method was performed to study the surface properties and optical properties of MB2 (M = Zr, V, Ta, Nb). The effects of different surface terminations are discussed, which indicates metal terminations have low work functions. The calculation of optical properties indicates that the four borides are suitable for spectral selective materials and optical storage materials. These findings provide valuable theoretical data for the design and application of MB2 in optoelectronic materials.

Application to nonlinear optical properties of the RSX-QIDH double-hybrid range-separated functional.

The effective calculation of static nonlinear optical properties requires a considerably high accuracy at a reasonable computational cost, to tackle challenging organic and inorganic systems acting as precursors and/or active layers of materials in (nano-)devices. That trade-off implies to obtain very accurate electronic energies in the presence of externally applied electric fields to consequently obtain static polarizabilities ( ) and hyper-polarizabilities ( and ). Density functional theory is known to provide an excellent compromise between accuracy and computational cost, which is however largely impeded for these properties without introducing range-separation techniques. We thus explore here the ability of a modern (double-hybrid and range-separated) Range-Separated eXchange Quadratic Integrand Double-Hybrid exchange-correlation functional to compete in accuracy with more costly and/or tuned methods, thanks to its robust and parameter-free nature.

Electronic and Optical Properties of Double Perovskite Oxide LaFeWO6: A Theoretical Understanding from DFT Calculations

In recent years, double perovskite oxides have gained attention as promising candidates in the realms of solar cells and catalysis. By adjusting their composition and engineering the band gap, numerous materials are being developed for energy-related applications. Oxide perovskites offer the benefit of a longer carrier lifetime compared to halide perovskites, which is advantageous for energy applications. In this study, we present a systematic theoretical analysis of a double perovskite oxide, examining his composition. The associated electronic and optical properties are discussed, along with prospects for identifying highly efficient materials within this family. This paper reports the study of electronic and optical properties of double perovskite oxide LaFeWO6 by utilizing the FP − LAPW method within the framework of (DFT). Results of density of states and energy bands are presented. The direct band gaps have been found for the systems by using the GGA approximation. Calculations of optical properties is also presented by considering the variations of optical parameters as a function of incident photon energy. The results indicate that LaFeWO6 exhibits a suitable band gap (0.71eV) for visible light absorption, along with promising electronic properties, making it a candidate for photocatalytic and photovoltaic applications.

Calculation of structural, electronic, magnetic and optical properties of C3N monolayer substituted with magnesium

In this article, Mg impurity effect on structural, electronic, magnetic and optical properties of C3N monolayer have been investigated using first principles calculations in the density functional theory framework utilizing Wien2K computational code. The results provide that the impurity added to the C3N monolayer changes the nature of the C3N monolayer to create magnetic half-metallic properties with 0.99 magnetization. By investigating the mechanical stability of these two structures, it is observed that the pure C3N structure is more stable than the Mg-substituted structure. Moreover, optical properties such as dielectric function, reflection coefficient, energy loss function, absorption coefficient and optical conductivity were calculated. The pure C3N monolayer and the C3N with Mg impurity are both optically anisotropic, leading to birefringence for the pure and substituted states. The results also provide a basic understanding of the design of composite structures applied in nanodevices based on two-dimensional advanced materials which is used in the spintronics industry.

Influence of different terminations on the surface properties of rare earth sesquioxides: first-principle calculations

Rare earth sesquioxide (R2O3) have attracted significant attention because of their stable surface and operable optical properties. In this paper, we comprehensively analyze the surface and optical properties of five rare earth sesquioxides (R2O3, where R = Sc, Y, La, Sm, Dy) using the first-principles method. The obtained results are consistent with other theoretical and experimental values. It is observed that the R terminated surfaces of R2O3 exhibits the lowest work function while the mixed atom terminations have the lowest surface energy, indicating their potential as electron emission materials. Additionally, calculations of optical properties reveal that R2O3 exhibits high reflectivity and optical absorption in the far ultraviolet region. Notably, Y2O3 demonstrates a remarkable 95% reflectivity in the far ultraviolet region, highlighting the immense potential of R2O3 in designing and applying optical devices. The theoretical calculation data in this paper provide a theoretical basis for related experiments.

A new method for measuring fast aggregation rate based on the growth of the colloidal aggregate size

We propose a novel technique to determine the absolute fast aggregation rate directly from the growth curve of the aggregate size. Our approach is convenient and effective as it eliminates the need for calculations of optical properties and does not require a precise zero point of aggregation time, which are both essential in traditional light-scattering methods. Through comparisons with conventional turbidity measurements, the reliability and precision of this new approach are verified for both homogeneous and heterogeneous aggregation.

First-principles calculations investigating structural, electronic optical and elastic properties of ABSe3 (A = Rb, Cs) compounds explored for photovoltaic and optoelectronics applications

In few recent years, great and significant efforts are devoted from researcher all over the world to pursue the revolution of photovoltaic’s materials and their uses in various applications. In the present work, a series of ab-initio simulations based on the density functional theory DFT plane wave pseudo-potential (PW-PP) method and hence performed towards the perselenoborate materials ABSe3 (A = Rb,Cs) for the first time along the three main polarizations of the incident wave directions [100], [010] and [001] with the aim of exploring their structural, electronic, optical and elastic properties. The generalized gradient approximation Perdew–Burke–Ernzerhof (GGA-PBE) carried out with CASTEP code is used for the exchange–correlation potential. The computed results showed that the structural properties of investigated compounds are very good agreement to the available experimental data, showing that the current calculations are quite accurate. Moreover, the density of states and electronic band structure calculations reveal that RbBSe3 (CsBSe3) compounds exhibit direct band gap semiconductor nature 1.66 eV (1,82 eV) respectively within the optimal range band gap 1eV–2eV required for photovoltaic’s applications makes them having great potential to obtain efficient Perovskite solar cell PSC. Additionally, our finding optical properties calculations reveal that the two investigated compounds exhibit strong absorption (prominent absorption peaks up 2,4 × 105cm−1) in UV range, while the real part of the refractive index for RbBSe3 (CsBSe3) was 2.62 (2.60) respectively which might be beneficial for photovoltaic application (top cell in solar cell) and optical applications. Also, high optical conductivity (∼1015sec−1) is found to be observed in visible ultraviolet range (1.7 eV to 30 eV). The lower reflectivity seen by RbBSe3 compared to CsBSe3 in the larger energy spectrum of electromagnetic radiation suggests that RbBSe3 compound is more suitable for electronic applications. Further, once the elastic constants are obtained, the calculated mechanical properties, bulk modulus (B), shear modulus (G), the ratio B/G, Young’s modulus (E), Poisson’s ratio (ν), anisotropy universal (AU) are calculated. Our calculated Young’s modulus indicate that the CsBSe3 is less hardness compared to RbBSe3, while Poisson’s ratio calculated leads them to have a character ionic and RbBSe3 is more ductile than CsBSe3. The calculation value of θ D predicted from elastic constants appears low which is closely related to many physical properties such as specific heat and melting temperature. Finally, the finding results reveal another way of investigating mechanical stability, where both compounds are mechanically stable since all elastic constant computed are perfectly satisfied the Born stability criteria, flexible and brittle. Finally, we hope that all these results will be helpful for designing photovoltaic and optoelectronic devices.

Calculation of Mechanical Properties, Electronic Structure and Optical Properties of CsPbX3 (X = F, Cl, Br, I).

We utilized a first-principle density functional theory for a comprehensive analysis of CsPbX3 (X = F, Cl, Br, I) to explore its physical and chemical properties, including its mechanical behavior, electronic structure and optical properties. Calculations show that all four materials have good stability, modulus of elasticity, hardness and wear resistance. Additionally, CsPbX3 demonstrates a vertical electron leap and serves as a semiconductor material with direct band gaps of 3.600 eV, 3.111 eV, 2.538 eV and 2.085 eV. In examining its optical properties, we observed that the real and imaginary components of the dielectric function exhibit peaks within the low-energy range. Furthermore, the dielectric function gradually decreases as the photon energy increases. The absorption spectrum reveals that the CsPbX3 material exhibits the highest UV light absorption, and as X changes (with the increase in atomic radius within the halogen group of elements), the light absorption undergoes a red shift, becoming stronger and enhancing light utilization. These properties underscore the material's potential for application in microelectronic and optoelectronic device production. Moreover, they provide a theoretical reference for future investigations into CsPbX3 materials.

Effect of Co-Doping on the Photoelectric Properties of the Novel Two-Dimensional Material Borophene

Borophene is a novel two-dimensional material with abundant crystal structure and photoelectric properties. We focus on the effect of co-doping on the electronic structure and optical properties of borophene using the first-principles method. The results show that the structure of Al and Ga co-doped borophene is obviously distorted because Al and Ga atoms have formed bonds with a bond length of 2.378 Å, and the two B atoms that bond together with Al and Ga are no longer formed bonds. However, it is also a two-dimensional planar structure after co-doping. After co-doping, the band gap width of the borophene system is narrowed from 1.409 eV to 1.376 eV, and the band gap is narrowed by 0.033 eV. Mulliken population analysis shows an obvious charge transfer between Al-B and Ga-B atoms in the co-doped borophene. The calculation of optical properties shows that the static dielectric constant ε1 (0) increases from 5.08 to 7.01, and ε2 (ω) is larger than that of the undoped sample in the low-energy range. Thus, the co-doping of Al and Ga can enhance the electromagnetic energy storage capacity and the visible light absorption ability. Although the reflectance of borophene is reduced by co-doping (the peak of the reflectivity can be decreased from 71% to 61% at E = 2.94 eV), it still presents metallic reflection characteristics. The static refractive index n0 can be increased from 2.25 to 2.65 by co-doping. The extinction coefficient shows strong band edge absorption at the low-energy range with an absorption edge of 0.85 eV. The light loss is limited to a very narrow energy range of approximately 7.30 eV, which indicates that borophene co-doped with Al and Ga can also be used as a light storage material. The optical conductivity reaches its maximum at E = 1.78 eV and 2.52 eV, which correspond to the light irradiation with a wavelength of 698 nm (red light) and 492 nm (cyan light), respectively. The results show that the Al-Ga co-doped borophene is sensitive to cyan light and red light, so it can be used to make photosensitive devices. The results can hopefully fill the gap in the application of borophene in semiconductor photoelectric devices and provide a theoretical basis for its application.

Ab initio calculations of electronic, magnetic, optical, and photocatalytic properties of strained 1T–ZrSe[formula omitted]

Because transition metal dichalcogenides (TMDs) can withstand high strain, strain engineering has shown to be an attractive strategy for modulating TMD characteristics and improving device performance. Density functional theory (DFT) was used to perform first-principles calculations on the electronic, magnetic, optical, and photocatalytic properties of a 1T–ZrSe2 monolayer under biaxial compressive and tensile strain. The first-principles computations revealed that all stressed structures experienced a semiconducting to metallic phase transition. Compressive strain resulted in no magnetization, whereas increasing tensile strain resulted in a significant increase in magnetization on 1T–ZrSe2. When 6% tensile strain was applied, the total magnetization changed 3.33 times, from 0.069 μB/cell to 0.184 μB/cell. Dynamic stability was maintained as the compressive strain was increased. However, dynamic stability held up to 10% of applied tensile strain. The vibration peak in Raman spectra shifted to a higher wavenumber which signifies the frequency reduction behavior with increasing tensile strain applied on 1T–ZrSe2. For different high–symmetry adsorption sites of I2 and I–Br on -10% strained 1T–ZrSe2, a noticeable band gap occurred and metallic to semiconducting phase transition was obtained. The bridge site of I2 exhibited significant adsorption energy among all the adsorption sites. This investigation satisfied the oxygen evaluation reaction (OER) condition for all adsorption sites of I2 and I–Br. The findings of this study will come up with novel schemes for 2D–TMD functional materials in numerous applications and propel the research interest in making spintronic and photocatalytic devices.

First-principles calculations of structural, electronic, optical and thermoelectric properties of doped binary chalcogenides Sn1-xAxSe (A= Au and Ag) for energy applications

The first-principles based DFT calculations were used to investigate the effect of transition metal (TM) doping on structural, electronic, optical and thermoelectric properties of Sn1-xAxSe (A = Au and Ag). The PBE-GGA approximation is used to calculate ground state properties of TM doped SnSe. These compounds show the presence of type-II intermediate band (IB) at Fermi level. A considerable energy bandgap is present between IB and conduction band. Significant contributions from Ag/Au and Se-atom in valence bands of Sn1-xAxSe (A = Au and Ag) are evident from presented DOS spectra. The calculated Fermi surfaces and Seebeck coefficient (S) confirms p-type nature of these semiconductors. From ε2(ω) spectra, it is evident that Sn1-xAxSe (A = Au and Ag) absorbs maximum number of incident photons in infrared (at ∼0.5 eV) and visible (at ∼2.2 eV) regions. The calculated values of n(ω) are 2.27 and 2.58 for Sn1-xAgxSe and Sn1-xAuxSe, respectively. We can confirm that Sn1-xAxSe (A = Au and Ag) are promising candidates for energy applications (especially solar cells) based on their optoelectronic and thermoelectric properties.

Synthesis, Characterization and Calculations of Linear and Nonlinear Optical Properties of Acrylonitrile Substituted Spirocyclotriphosphazene Derivatives

There methoxy-substituted acrylonitrile compounds (2a, 2b and 2c) were synthesized using method described in the literature. Compounds 3a, 3b and 3c were obtained by using the microwave demethylation method for the first time, then they were reacted with 2,2-dichloro-4,4,6,6-bis[spiro(2′,2″-dioxy-1′,1″-biphenylyl)]-cyclotriphosphazene (DPP) to reach final products 4a, 4b and 4c. The structures of the substituted compounds were determined by elemental analysis, MALDI-TOF, 1H, [Formula: see text]C APT, [Formula: see text]P NMR and FT-IR spectroscopy. In order to investigate the usability potential of the synthesized products 4a, 4b and 4c in optoelectronic devices, we experimentally measured the band gaps and calculated their nonlinear optical properties by Density Functional Theory (DFT) method. Obtained results showed that the introduction of an electronegative substituent (F) or an electropositive substituent (CH[Formula: see text] to the parent compound 4a has minimal impact on the absorption spectra. However, the fluorine-substituted compound 4b exhibits considerably higher values in terms of dipole moment, averaged polarizability, and first-hyper polarizability when compared to compounds 4a and 4c. Calculated values of dipole moment, averaged polarizability, first-hyper polarizability, electronegativity and global hardness of the fluorine-substituted compound 4b were found to be 6.281 (debye), −393.592 (1.4818 × 10[Formula: see text] cm[Formula: see text], 899.857 (8.641 × 10[Formula: see text] cm5/e.s.u), 4.492 (eV) and 1.922 (eV), respectively. These values were the highest in magnitude in comparison to the associated values of 4a and 4c. Overall results indicated that the influence of introducing an electropositive substituent (CH[Formula: see text] to the parent compound 4a, resulting in decreased stability and increased reactivity. Conversely, the introduction of an electronegative substituent (F) to 4a leads to opposite effects.

Electronic structure and optical absorption property of BaTiO3/BiCoO3

In this paper, we calculated the different forms of BaTiO3/BiCoO3 composite structure, predicting their visible light absorption performance based on the electronic structure using the first principles calculations. Firstly, six possible compounds that come from BaTiO3 and BiCoO3 were constructed. By calculating the different antiferromagnetic (AFM) structures of strip, columnar, and layered composite structures, it is found that the ground state of the composite structure changes to G‐type AFM structure from C‐type AFM structure of pure BiCoO3 under the influence of BaTiO3. Energy band calculations show that band gaps of three composite structures are smaller than those of pure BaTiO3 and pure BiCoO3. Furthermore, density of states analysis shows that the conduction band minimum (CBM) and valence band maximum (VBM) of three composite structures are mainly from the contribution of Co 3d and O 2p. For the characteristic that CBM and VBM of materials come from different atoms, it would reduce the recombination opportunities of electrons and holes and is conducive to the increase of photoelectric conversion efficiency under visible light irradiation. The calculation of optical properties shows that optical absorption coefficients of three composite structures are much larger than that of BaTiO3, especially the layered composite structure. There is a high absorption peak near 500 nm of the solar spectral irradiation maximum, which is significantly important to improve the optical energy conversion efficiency of the composite materials. The work provides an effective way for the application of wide band gap ferroelectric materials in ferroelectric photovoltaic.

First-Principles Calculation of Structural, Electronic, and Optical Properties of Cubic Perovskite CsPbF3

Lead halide perovskites have attracted considerable attention as one of the most promising materials for optoelectronic applications. The structural, electronic, and optical properties of the cubic perovskite CsPbF3 were studied using density functional theory in conjunction with plane waves, norm-conserving pseudopotentials, and Perdew-Berg-Erzenhof flavor of generalized gradient approximation. The obtained structural parameters are a good agreement with the experimentally measured and other’s theoretically predicted values. The obtained electronic band structure revealed that cubic CsPbF3 has a direct fundamental band gap of 2.99 eV at point R. The calculated energy band gaps at the high symmetry points agree with the other available theoretical results. The GW method is adapted to correct the underestimated fundamental energy gap value to 4.05 eV. The contribution of the different bands was analyzed from the total and partial density of states. The electron densities show that Cs and F have strong ionic bonds, whereas Pb and F have strong covalent bonds. The optical properties of CsPbF3 were calculated using the density functional perturbation theory and Kramers-Kronig relations. The wide and direct bandgap nature and the calculated optical properties imply that cubic CsPbF3 can be used in optical and optoelectronic devices for high frequencies visible and low frequencies ultraviolet electromagnetic radiation.