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The extensive applications of MXenes, a novel type of layered materials known for their favorable characteristics, have sparked significant interest. This research focuses on investigating the influence of surface functionalization on the behavior of Mn2NTx (Tx=O2, F2) MXenes monolayers using the "Density functional theory (DFT) based full-potential linearized augmented-plane-wave (FP-LAPW)" method. We elucidate the differences in the physical properties of Mn2NTx through the influence of F and O surface functional groups. We found that O-termination results in half-metallic behavior, whereas the F-termination evolves metallic characteristics within these MXene systems. Similarly, surface termination has effectively influenced their optical absorption efficiency. For instance, Mn2NO2 and Mn2NF2 effectively absorb UV light ~50.15×104â cm-1 and 37.71×104â cm-1, respectively. Additionally, they demonstrated prominent refraction and reflection characteristics, which are comprehensively discussed in the present work. Our predictions offer valuable perspectives into the optical and electronic characteristics of Mn2NTx-based MXenes, presenting the promising potential for implementing them in diverse optoelectronic devices.
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This study aims to simulate a therapeutic plan for a normal human blood model under various patho-physiological conditions, such as the development of leukemia/blood diseases, by means of Monte Carlo multilayered simulation. The photosensitizing compound selectively accumulates in the target cells. A superficial treatment of a blood sample was performed at different ratios of oxygen saturation ([Formula: see text]) under the concentration ([Formula: see text] = 30 µM) effect of merocyanine 540 (MC540) in the blood irradiation. This was done under the application of visible light of wavelength ~ [Formula: see text] at an exposure time ~ 60 s. The dose of photodynamic therapy (PDT) was evaluated for the biological damage, leading to necrosis and blood damage during the treatment. In addition, the effect of PDT treatment response in the blood is related to hemoglobin oxygen saturation, resulting in an excellent relationship between the changes caused by the treatment in the blood at a peculiar oxygen saturation rate (for the highest response: [Formula: see text] 50%) and a light dose (LD) of 3.83 [Formula: see text] above the minimal toxicity of normal tissues. The photodynamic dose is related to the depth of necrosis and the time of treatment for the achievement of the LD delivery at the PDT of blood.
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Fotoquimioterapia , Simulação por Computador , Humanos , Luz , Método de Monte Carlo , Fotoquimioterapia/métodos , Fármacos FotossensibilizantesRESUMO
Advanced computational approaches have made the design and characterization of novel two-dimensional (2D) materials possible for applications in cutting-edge technologies. In this work, we designed five polymorphs of 2D tin sulfide (namely, α-SnS, ß-SnS, γ-SnS, δ-SnS, and ε-SnS) and explored their potential for thermoelectric applications using density functional theory-based computational approaches. Investigations of the energetic stability showed that the generated monolayers were as stable as parent α-SnS and exhibited cohesive and formation energies comparable to those of other stable 2D materials. These monolayers demonstrated high structural anisotropy (except ß-SnS), which resulted in interesting features in the effective mass of the charge carriers and the subsequent thermoelectric properties. The in-plane anisotropy yielded different effective masses of charge carriers along the 100- and 010-directions. The x- and y-components of the electrical conductivity tensors were accordingly enhanced by the p-type doping and n-type doping, respectively. We estimated the maximum thermoelectric power factors along the x- and y-axes and the corresponding optimal doping levels were recognized; this suggested that the thermoelectric performance of these monolayers along the x-direction can be improved by p-type doping and that along the y-direction can be improved by n-type doping. Moreover, the thermoelectric figures of merit of the SnS monolayers approached a benchmark value of unity at room temperature. Our results suggested that these novel polymorphs of 2D SnS are promising materials for applications in direction-dependent thermoelectric devices. The present study can provide valuable guidance for generating low-cost and non-toxic polymorphs of other layered-structure materials.
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Radiotherapy is an extensively used treatment for most tumor types. However, ionizing radiation does not discriminate between cancerous and normal cells surrounding the tumor, which can be considered as a dose-limiting factor. This can lead to the reduction of the effectiveness of tumor cell eradication with this treatment. A potential solution to this problem is loading the tumor with high-Z materials prior to radiotherapy as this can induce higher toxicity in tumor cells compared to normal ones. New advances in nanotechnology have introduced the promising use of heavy metal nanoparticles to enhance tumor treatment. The primary studies showed that gold nanoparticles (GNPs) have unique characteristics as biocompatible radiosensitizers for tumor cells. This study aimed to quantify the dose enhancement effect and its radial dose distribution by Monte Carlo simulations utilizing the EGSnrc code for the water-gold phantom loaded with seven different concentrations of Au: 0, 7, 18, 30, 50, 75, and 100 mg-Au/g-water. The phantom was irradiated with two different radionuclide sources, Ir-192 and Cs-137, which are commonly used in brachytherapy, for all concentrations. The results exhibited that gold nanoparticle-aided radiotherapy (GNRT) increases the efficacy of radiotherapy with low-energy photon sources accompanied with high Au concentration loads of up to 30 mg-Au/g-water. Our finding conducts also to the detection of dose enhancement effects in a short average range of 650 µm outside the region loaded with Au. This can indicate that the location determination is highly important in this treatment method.
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Ouro/química , Nanopartículas Metálicas/química , Método de Monte Carlo , Neoplasias/radioterapia , Radioisótopos de Césio/química , Simulação por Computador , Relação Dose-Resposta à Radiação , Radioisótopos de Irídio/química , Imagens de Fantasmas , Dosagem RadioterapêuticaRESUMO
Spin-polarized transport properties are determined for pentacene sandwiched between Ni surface electrodes with various anchoring ligands. These calculations are carried out using spin density functional theory in tandem with a non-equilibrium Green's function technique. The presence of a Se atom at the edge of the pentacene molecule significantly modifies the transport properties of the device because Se has a different electronegativity than S. Our theoretical results clearly show a larger current for spin-up electrons than for spin-down electrons in the molecular junction that is attached asymmetrically across the Se linker at one side of the Ni electrodes (in an APL magnetic orientation). Moreover, this molecular junction exhibits pronounced NDR as the bias voltage is increased from 0.8 to 1.0 V. However, this novel NDR behavior is only detected in this promising pentacene molecular device. The NDR in the current-voltage (I-V) curve results from the narrowness of the density of states for the molecular states. The feasibility of controlling the TMR is also predicted in these molecular device nanostructures. Spin-dependent transmission calculations show that the sign and strength of the current-bias voltage characteristics and the TMR could be tailored for the organic molecule devices. These molecular junctions are joined symmetrically and asymmetrically between Ni metallic probes across the S and Se atoms (at the ends of the edges of the pentacene molecule). Our theoretical findings show that spin-valve phenomena can occur in these prototypical molecular junctions. The TMR and NDR results show that nanoscale junctions with spin valves could play a vital role in the production of novel functional molecular devices.
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The precise manipulation of electromagnetic and thermoelectric characteristics in the miniaturization of electronic devices offers a promising foundation for practical applications in quantum computing. Double perovskites characterized by stability, non-toxicity, and spin polarization, have emerged as appealing candidates for spintronic applications. This study explores the theoretical elucidation of the influence of iridium's 5d electrons on the magnetic characteristics of Sr2AIrO6 (A = Y, Lu, Sc) with WIEN2k code. The determined formation energies confirm the thermodynamic stability while an analysis of band structure and the density of states (DOS) reveals a half-metallic ferromagnetic character. This characteristic is comprehensible through the analysis of exchange constants and exchange energies. The current analysis suggests that crystal field effects, a fundamental hybridization process and exchange energies contribute to the emergence of ferromagnetism due to electron-spin interactions. Finally, assessments of electrical and thermal conductivities, Seebeck coefficient, power factor, figure of merit and magnetic susceptibility are conducted to assess the potential of the investigated materials for the applications in thermoelectric devices.
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Vacancy-ordered double perovskites (DPs) are emerging materials for spintronics due to their stable structures and non-toxic properties. In this study, we conducted a comprehensive investigation into the role of 4d electrons in Tc to understand their impact on the ferromagnetic properties of K2TcY6 (Y = Cl, Br). We have employed a modified Back and Johnson potential to assess electronic and magnetic characteristics and utilized the BoltzTraP code to investigate thermoelectric effects. Experimental lattice constants confirmed the presence of stable structures and formation energy estimates affirmed their thermodynamic stability. The Heisenberg model and density of electron states (DOS) at the Fermi level provides insights into Curie temperature and spin polarization. The presence of ferromagnetism is evident in the density of states, reflecting the transition of electron spins that support the exchange mechanism. The study delves into how electron functionality influences the control of ferromagnetism, considering exchange constants, exchange energies, hybridization process and the crystal field energies. Moreover, the exploitation of magnetic moments from Tc to K and Cl/Br sites takes precedence in driving ferromagnetism by exchanging electron spins rather than forming magnetic clusters. Additionally, to explore the optical characteristics of the compounds, we investigated their optical absorption, dielectric constants and refractive index within the energy range of 0-10 eV, ensuring absorption across both the visible and ultraviolet regions. Finally, we delve into the impact of the thermoelectric effect on both thermoelectric performance and spin functionality, taking into account factors such as the Seebeck coefficient, power factor, and electronic conductivity.
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Recent studies have reported that lead-halide perovskites are the most efficient energy-harvesting materials. Regardless of their high-output energy and structural stability, lead-based products have risk factors due to their toxicity. Therefore, lead-free perovskites that offer green energy are the expected alternatives. We have taken CsGeX3(X = Cl, Br, and I) as lead-free halide perovskites despite knowing the low power conversion rate. Herein, we have tried to study the mechanisms of enhancement of energy-harvesting capabilities involving an interplay between structure and electronic properties. A density functional theory simulation of these materials shows a decrease in the band gaps, lattice parameters, and volumes with increasing applied pressure. We report the high piezoelectric responses and high electro-mechanical conversion rates, which are intriguing for generating electricity through mechanical stress.
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The recent discovery of superconductivity behavior in the mother BiS2-layered compounds has captivated the attention of several physicists. The crystal structure of superconductors with alternate layers of BiS2 is homologous to that of cuprates and Fe-based superconductors. The full-potential linearized augmented plane-wave (FP-LAPW) technique was utilized to investigate the electronic structures and density of states in the vicinity of the Fermi energy of SrFBiS2 and BaFBiS2 compounds under the electron carriers doping. The introduction of electron doping (carries doping) reveals that the host compounds SrFBiS2 and BaFBiS2 exhibit features indicative of superconductivity. This carrier doping of SrFBiS2 and BaFBiS2 compounds (electron-doped) has a significant impact on the lowest conduction states near the Fermi level for the emergence of the superconducting aspect. The electron doping modifies and induces changes in the electronic structures with superconducting behavior in (Ae)1.7FBiS2(Ae=Sr,Ba) compounds. A Fermi surface nesting occurred under the modification of electrons (carriers) doping in the host compounds SrFBiS2 and BaFBiS2. Furthermore, the optical characteristics of the carrier-doped SrFBiS2 and BaFBiS2 compounds are simulated. Due to the anisotropic behavior, the optical properties of these materials based on BiS2 demonstrate a pronounced polarization dependency. The starting point at zero photon energy in the infrared region is elucidated by considering the Drude features in the optical conductivity spectra of SrFBiS2 and BaFBiS2 compounds, when the electron carriers doping is applied. It was clearly noticed that the spin-orbit coupling (SOC) influences the electronic band structures, density of states, Femi surface, and optical features because of the heavy Bismuth atom, which may disclose fascinating aspects. Further, we conducted simulations to assess the thermoelectric properties of these mother compounds. The two BiS2-layered compounds could be suitable for practical thermoelectric purposes and are highlighted through assessment of electrical conductivity, thermal conductivity, Seebeck coefficient, and power factor. As a result, we propose that the mechanisms of superconducting behavior in BiS2 family may pave new avenues for investigating the field of unconventional superconductivity. It may also provide new insights into the origin of high-Tc superconductivity nature.
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Bismuto , Eletrônica , Condutividade Elétrica , Anisotropia , ElétronsRESUMO
We investigate the structural, electronic and dynamical properties of ZnSe liquid using tight-binding molecular dynamics (TBMD) simulations. We report the TBMD calculations for the solid and liquid forms of the ZnSe compound. To produce more realistic results the TB model includes the local environment dependence in the Hamiltonian matrix at finite temperature for ZnSe. To further demonstrate the efficiency of the TBMD approach, we present results for finite temperature physical properties of ZnSe liquid. We are able to show good agreement with experiment for the atomic mean-squared displacement and melting point.
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Simulação de Dinâmica Molecular , Compostos de Selênio/química , Compostos de Zinco/químicaRESUMO
We present the magnetic and optical properties of various combinations of ordered spin state configurations between low-spin (LS) state, intermediate-spin (IS) state, and high-spin (HS) state of LaCoO(3) . In this study, we use the state-of-the-art first principles calculations based on generalized gradient (GGA) + Hubbard U approach. The excited-state properties of different spin configurations of LaCoO(3) such as the X-ray absorption spectra, optical conductivity, reflectivity, and electron energy loss are calculated. We have demonstrated that the optical spectra results can be used for analyzing the spin state of Co(3+) ion. The first specie is the local excitation of IS cobalt ions in the LS ground state. The second excitation leads to the stabilization of the mixed IS/HS Co(3+) metallic state. At low temperature, the comparison between O 2p and Co 3d projected density of states with the experimental valence band spectra indicates significant IS Co(3+) ions and this is in sharp contrast to the HS state which is negligible. The line shape of O 2s and Co 3d core level spectra are well reproduced in this study. The present results are in excellent agreement with the available experimental data. The variation in the spectra of different configurations of LaCoO(3) suggests a changing in the spin state as the temperature is enhanced from 90 to 500 K.
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Low cost and highly efficient two dimensional materials as photocatalysts are gaining much attention to utilize solar energy for water splitting and produce hydrogen fuel as an alternative to deal with the energy crisis and reduce environmental hazards. First principles calculations are performed to investigate the electronic, optical and photocatalytic properties of novel two dimensional transition metal dipnictide XP2 (X = Ti, Zr, Hf) monolayers. The studied single layer XP2 is found to be dynamically and thermally stable. TiP2, ZrP2 and HfP2 systems exhibit semiconducting nature with moderate indirect band gap values of 1.72 eV, 1.43 eV and 2.02 eV, respectively. The solar light absorption is found to be in energy range of 1.65-3.3 eV. All three XP2 systems (at pH = 7) and the HfP2 monolayer (at pH = 0) that straddle the redox potentials, are promising candidates for the water splitting reaction. These findings enrich the two dimensional family and provide a platform to design novel devices for emerging optoelectronic and photovoltaic applications.
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The strategy of stacking two-dimensional materials for designing van der Waals heterostructures has gained tremendous attention in realizing innovative device applications in optoelectronics and renewable energy sources. Here, we performed the first principles calculations of the geometry, optoelectronic and photocatalytic performance of MS2-CrSSe (M = Mo, W) vdW heterostructures. The mirror asymmetry in the Janus CrSSe system allows the designing of two models of the MS2-CrSSe system by replacing S/Se atoms at opposite surfaces in CrSSe. The feasible configurations of both models of the MS2-CrSSe system are found energetically, dynamically and thermally stable. The studied heterobilayers possess an indirect type-I band alignment, indicating that the recombination of photogenerated electrons and holes in the CrSSe monolayer is hence crucial for photodetectors and laser applications. Remarkably, a red-shift in the optical absorption spectra of MS2-CrSSe makes them potential candidates for light harvesting applications. More interestingly, all heterobilayers (except W(Mo)S2-CrSSe of model-I(II)) reveal appropriate band edge positions of the oxidation and reduction potentials of the photocatalysis of water dissociation into H+/H2 and O2/H2O at pH = 0. These results shed light on the practical design of the MS2-CrSSe system for efficient optoelectronic and photocatalytic water splitting applications.
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Full Heuslers alloys are a fascinating class of materials leading to many technological applications. These have been studied widely under ambient conditions. However, less attention been paid to study them under the effect of compression and strain. Here in this work Co2YZ (Y= Cr, Nb, Ta, V and Z = Al, Ga) Heusler alloys have been studied comprehensively under pressure variations. Calculated lattice constants are in reasonable agreement with the available data. It is determined that lattice constant deceases with the increase in tensile stress and increases by increasing pressure in reverse direction. Band profiles reveals the half metallic nature of the studied compounds. The bond length decreases while band gap increases in compressive strain. The compounds are found to be reflective in visible region, as characteristics of the metals. The magnetic moments reveal the half-mettalic ferromagnetic nature of the compounds.
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Ligas , Nióbio , PressãoRESUMO
A first-principle computational method has been used to investigate the effects of Ru dopants on the electronic and optical absorption properties of marcasite FeS2. In addition, we have also revealed a new marcasite phase in RuS2, unlike most studied pyrite structures. The new phase has fulfilled all the necessary criteria of structural stability and its practical existence. The transition pressure of 8 GPa drives the structural change from pyrite to orthorhombic phase in RuS2. From the thermodynamical calculation, we have reported the stability of new-phase under various ranges of applied pressure and temperature. Further, from the results of phonon dispersion calculated at Zero Point Energy, pyrite structure exhibits ground state stability and the marcasite phase has all modes of frequencies positive. The newly proposed phase is a semiconductor with a band gap comparable to its pyrite counterpart but vary in optical absorption by around 106 cm-1. The various Ru doped structures have also shown similar optical absorption spectra in the same order of magnitude. We have used crystal field theory to explain high optical absorption which is due to the involvement of different electronic states in formation of electronic and optical band gaps. LÓ§wdin charge analysis is used over the customarily Mulliken charges to predict 89% of covalence in the compound. Our results indicate the importance of new phase to enhance the efficiency of photovoltaic materials for practical applications.
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HgTe/CdTe superlattices (SLs), have emerged as unprecedented materials with tremendous functionalities, such as solar photocell devices. We carried out first-principles analyses in the framework of the full-potential linearized augmented plane wave (FP-LAPW) scheme to understand the impact of layer periodicity and strain on HgTe/CdTe superlattices. This technique allows us to describe the electronic and optical features of low dimensional systems, such as CdTe-HgTe heterojunctions. Alteration of the layer thickness and strain is imperative for tailoring the energy band gap of HgTe/CdTe superlattices. Thus, the CdTe and HgTe layers possess an appreciable influence on the induced forbidden gap of SLs because of their distinct quantum confinement characteristics. The electronic structures illustrate that the alteration in HgTe and CdTe layer thickness is pivotal for the overlap or non-overlap of the conduction bands and valence bands. Indeed, these systems can yield a semi-metallic or normal state with significant modification in the optical absorption of HgTe/CdTe SLs with respect to their bulk counterparts. Such SL systems have several advantageous features, involving their tailorable near band edge optical properties. Hence, it is feasible to optimize the requisite characteristics for electronic devices based on these SLs. This may enhance the development of HgTe/CdTe SLs in vast applications envisioned in infrared devices.
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The structural and mechanical stability of Fe2TaAl and Fe2TaGa alloys along with the electronic properties are explored with the help of density functional theory. On applying different approximations, the enhancement of semiconducting gap follows the trend as GGA < mBJ < GGA + U. The maximum forbidden gaps observed by GGA + U method are Eg = 1.80 eV for Fe2TaAl and 1.30 eV for Fe2TaGa. The elastic parameters are simulated to determine the strength and ductile nature of these materials. The phonon calculations determine the dynamical stability of all these materials because of the absence of any negative frequencies. Basic understandings of structural, elastic, mechanical and phonon properties of these alloys are studied first time in this report.
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The electronic, optical and thermoelectric analyses of BaGeO3 perovskite have been done by using density functional theory (DFT) based Trans and Blaha modified Becke and Johnson (TB-mBJ) approach. The applied pressure (up to 30â¯GPa) has been found tailoring the band gap from indirect to direct bandgap (at 20â¯GPa), within the visible region, revealing renewable energy applications of the studied perovskite. The applied pressure improves mechanical stability by increasing ductility. Furthermore, optical properties are illustrated by computing dielectric constants, refraction, absorption, optical conductivity and optical loss factor for suggesting optoelectronic applications. The maximum peaks shifting to higher energy, due to increasing pressure indicate a blue shift. Finally, the calculated thermal and electrical conductivities, See-beck coefficient, power factor, Hall coefficient, specific heat capacity, susceptibility and electron densities are also elaborated for thermoelectric applications by using BoltzTraP code.
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Compostos de Cálcio/química , Óxidos/química , Pressão , Energia Renovável , Titânio/química , Condutividade Elétrica , Eletrônica , Modelos Teóricos , Semicondutores , Análise Espectral , Condutividade TérmicaRESUMO
We have computed the electronic structure and transport properties of Fe2TaZ (Z = Al, Ga, In) alloys by the full-potential linearized augmented plane wave (FPLAPW) method. The magnetic conduct in accordance with the Slater-Pauling rule classifies them as non-magnetic alloys with total zero magnetic moment. The semiconducting band profile and the density of states in the post DFT treatment are used to estimate the relations among various transport parameters such as Seebeck coefficient, electrical conductivity, thermal conductivity, and figure of merit. The Seebeck coefficient variation and band profiles describe the p-type behavior of charge carriers. The electrical and thermal conductivity plots follow the semiconducting nature of bands along the Fermi level. The overall measurements show that semi-classical Boltzmann transport theory has well-behaved potential in predicting the transport properties of such functional materials, which may find the possibility of their experimental synthesis for future applications in thermoelectric technologies.
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The magnetism of surfaces and interfaces can differ strongly from the magnetism of corresponding bulk materials. In the case of actinide systems the study of the surfaces and interfaces is still at the very beginning. In this work, we investigated the electronic and magnetic properties of U films and U(001)(1)/Fe(110)(3) multilayers within the framework of the density functional theory. We report both scalar-relativistic and fully relativistic calculations. The exchange correlation potential was treated in the generalized gradient approximation (GGA). In agreement with previous calculation by Stojic et al (2003 Phys. Rev. B 68 094407) we obtained the surface layer of the U films to be magnetic for the bulk lattice parameter. The dependence of the magnetic properties of the U films on the lattice parameter was studied. It is shown that decreasing distances between U atoms lead to decreasing magnetic moment and finally to the nonmagnetic ground state. The variation of the magnetic moment as a function of the lattice parameter is discontinuous. Using the frozen-magnon approach we evaluated the parameters of the inter-atomic exchange interactions and estimated the Curie temperature. The calculation for U(001)(1)/Fe(110)(3) multilayers showed that the U layer is magnetic with the direction of the U moments opposite to the Fe moments. The importance of the U-Fe hybridization is revealed. Both the intra-layer (U-U, Fe-Fe) and inter-layer (U-Fe) exchange interactions were evaluated. The temperature dependence of the layer magnetizations was studied within the random-phase approximation for the Heisenberg Hamiltonian for classical spins.