Density Of States Analysis Research Articles

Adsorption and gas sensitivity properties of graphene and Rh-decorated graphene towards SF6 decomposed gases: A DFT study

In order to solve the serious threat of SF6 decomposed gases (H2S, SO2, SOF2, SO2F2) to the stable operation of electrical equipment. In this study, the geometric structure, adsorption energy, density of states (DOS), sensitivity based on band structure and recovery time of H2S, SO2, SOF2, SO2F2 on graphene and Rh-modified graphene (Rh-graphene) were investigated computationally by density functional theory (DFT). The geometric structure of Rh-graphene was optimized with an average Rh-C bond length of 1.891 Å. According to the analysis of DOS and band structure, the electrical conductivity has a little effect of the Rh-graphene compared with pristine graphene, but Rh modification can regulate the band gap of graphene. The adsorption energy (Ead) and the sensitivity (S) at work temperature indicate that graphene has ideal adsorption and sensing properties for SO2 and Rh-graphene reflects the excellent applicability as the SO2 and SO2F2 gases sensor with the sensitivity of approximately −99 % and −60 %, respectively. The Graphene/SO2 system owns the minimum recovery time of 2154.3 ps. The recovery time of Rh-graphene/H2S and SOF2 is several orders of magnitude smaller than Rh-graphene/SO2 and SO2F2. The analysis of DOS and band structure was used to explain the sensing mechanism. The study would lay a theoretical foundation for the development of SF6 decomposed gases sensor for electrical equipment insulation.

Tailoring Si12C12 nanocluster with late first-row transition metals: A promising approach during single-atom catalysis toward hydrogen evolution reaction (HER)

Hydrogen evolution reaction (HER) has gained a great interest in recent years because it provides the cleanest fuel (H2). One of the most demanding things required for this reaction is an efficient and cost-effective catalyst. Single atom catalysis is one of the most remarkable strategies in this regard. Herein, transition metals adsorbed silicon carbide nanocages (TM@Si12C12; TM = Zn, Fe, Co, Cu, Ni) are investigated as single atom catalysts in order to search less expensive electrocatalysts with excellent efficiency for HER. The pure and hydrogen adsorbed TM@Si12C12 show geometric and thermodynamic stability which illustrates their practical utility. Interaction energies obtained range from −0.70 to −5.73 eV, and it is suggested that Cu@Si12C12 may play an excellent role in HER due to its lowest Gibbs free energy of −0.17 eV (near to zero). In this work, we investigated electronic properties through natural bond orbital (NBO) analysis of selected TM@SiC. According to NBO calculations, it is observed that charge is transferred from adsorbed transition metals towards nanocage. After H adsorption, NBO charge is transferred to hydrogen which shows the adsorption properties of H. In case of HOMO-LUMO energy gap, it is observed that transition metal adsorbed complexes have small energy gaps between 2.17 and 2.77 eV but after adsorption of hydrogen, this energy gap increases to lie in the range of to change from 2.93 to 3.12 eV, which also verified the electronic stability of H adsorbed species. The noncovalent interactions are estimated through NCI analysis. The density of states analysis gives insight about the energy states of occupied and unoccupied orbitals of electrons. The highest thermodynamic stability and electronic conductivity of transition metal adsorbed silicon carbide suggested it as an excellent supportive surface for HER.

Photoluminescence properties of Pr-doped LaAsO4: An experimental and theoretical study employing density functional theory

Praseodymium doped lanthanum arsenate, denoted as La1-xPrxAsO4, has been synthesized with different concentrations of the dopant (x = 0.5 %; 1 %; 2 %; 3 % and 5 %) via the combustion method and their optoelectronic properties have been investigated. A study of the crystalline structure and size of the compound by XRD confirms that both the pristine LaAsO4 and Pr-doped LaAsO4 are pure and maintain a monoclinic crystal structure, with the crystalline size ranging from 60 to 76 nm. The morphological study of the nanoparticles by SEM analysis reveals that all samples, regardless of the concentration of Pr3+, consist of homogeneously packed and irregularly shaped small particles. The optical studies by absorption and fluorescence spectroscopies highlight the unique optoelectronic characteristics of La1-xPrxAsO4, with absorption predominantly in the UV and blue regions and prominent emission peaks in the visible spectrum, most notably at 610 nm. The optimal luminescence is observed at a 0.5 % Pr3+ doping level, deviating from typical trends as higher concentrations lead to diminished emission intensity and lifetime due to concentration quenching effects. The application of Density Functional Theory (DFT) with GGA + PBE and GGA + PBE + U approximations has effectively elucidated the electronic structure and optical properties of the Pr-doped LaAsO4. The incorporation of Pr's 4f states within the LaAsO4 forbidden band significantly alters the material's electronic landscape, notably reducing the optical band gap from 4.45 eV to 2.299 eV. This modification in the band structure aligns favourably with the dielectric function curves and density of states analyses, corroborating the observed visible light emission in the doped samples.

Rational Design of Cost-Effective Metal-Doped ZrO2 for Oxygen Evolution Reaction

HighlightsSurface energy and surface Pourbaix diagram reveal that ZrO2 (1¯11\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\overline{1 }11$$\\end{document}) is the most thermodynamically stable facet and is preferentially occupied by HO* at the equilibrium potential of oxygen evolution reaction (OER).Microkinetic modeling analyzed the OER activity of 40 single-metal doped ZrO2 and identified 16 metals exhibit improved catalytic activity, with Rh and Fe dopants showing the remarkable improvement.Thermodynamic free energy diagrams, density of states analysis, and ab initio molecular dynamics simulations further confirm that Fe–ZrO2 and Rh–ZrO2 are highly promising catalysts for OER, showcasing low ΔG for the rate-determining step, high conductivity, and exceptional stability.

Use of benzothiophene ring to improve the photovoltaic efficacy of cyanopyridinone-based organic chromophores: a DFT study.

The benzothiophene based chromophores (A1D1-A1D5) with A-π-A configuration were designed via end-capped tailoring with benzothiophene type acceptors using reference compound (A1R). Quantum chemical calculations were accomplished at M06/6-311G(d,p) level to probe optoelectronic and photophysical properties of designed chromophores. Therefore, frontier molecular orbitals (FMOs), binding energy (Eb), open circuit voltage (Voc), transition density matrix (TDM), density of state (DOS) and UV-Vis analyses of A1R and A1D1-A1D5 were accomplished. The designed compounds (A1D1-A1D5) exhibited absorption values in the visible region as 616.316-649.676 nm and 639.753-665.508 nm in gas and chloroform phase, respectively, comparing with reference chromophore. An efficient charge transference from HOMO towards LUMO was found in A1D1-A1D5 chromophores which was further supported by TDM and DOS analyses. Among all chromophores, A1D2 exhibited unique characteristics such as reduced band gap (2.354 eV), higher softness (σ = 0.424 eV), lower exciton binding energy (0.491 eV) and maximum value of open circuit voltage (Voc = 1.981 V). Consequently, A1D2 may be considered as potential candidate for the development of optoelectronic devices. These analyses revealed that the studied compounds exhibited promising findings. They may be utilized in the realm of organic solar cells.

DFT studies on structure, electronics, bonding nature, NBO analysis, thermodynamic properties, molecular docking, and MM-GBSA evaluation of 4-methyl-3-[2-(4-nitrophenyl)-1,3-dioxo-2,3-dihydro-1H-isoindole-5-amido]benzoic acid: a potent inhibitor of Graves’ disease

AbstractA calculation analysis on the molecular structure and energy of 4-methyl-3-[2-(4-nitrophenyl)-1,3-dioxo-2,3-dihydro-1H-isoindole-5-amido]benzoic acid (COD30) is carried out with the 6-311G (d,p) basis set by the DFT/RB3LYP method as an anti-graves' disease treatment. The calculated FT-IR spectrum is strongly correlated with the vibrational spectra reported in the literature. To evaluate the entire electron density and organic reactive sites of COD30, molecular electrostatic potential (MEP) and frontier molecular orbitals (FMO) were analyzed. The density of states analysis is used to determine the orbital molecular contributions (DOS and PDOS). In comparison to methimazole (MMI) and propylthiouracil, COD30 showed more encouraging docking results, and it also offered golden binding contacts in addition to an improvement in docking energy (PTU). The outcomes of bioactivity prediction and MD simulation indicate that COD30 could be further developed into an inhibitor of Graves' disease.

Computational modeling of oligothiophenes‐based donor molecules to boost optoelectronic attributes of organic solar cells

AbstractThe computational modeling of seven oligothiophene‐based donor molecules (TZ1–TZ7) designed by acceptor modification at the terminal position of the literature molecule (TZR) were discussed for organic solar cells (OSCs). DFT simulations using B3LYP/def2svp levels were performed to study the optoelectronic, and PV properties of TZ1–TZ7. A range of essential aspects for efficient small donor molecules like open circuit voltages (VOC), excitation energy (Ex), dipole moment (μ), density of state (DOS), absorption maxima (λmax), transition density matrix (TDM), binding energy (Eb), and frontier molecular orbitals (FMOs) of TZ1–TZ7 and TZR have also been investigated. DOS and FMOs analysis revealed a reduced energy gap (Eg) and effective charge transfer (CT) in the TZ1–TZ7 molecules. The absorption spectra were examined using TD‐DFT. Due to smaller Eg, Eb, Ex, and higher λmax, μ, the TZ1–TZ7 molecules exhibit remarkable optoelectronic properties. The computed VOC (0.969–1.189) and fill factor (0.886–0.897) for TZ1–TZ7 lead to improved power conversion efficiency (PCE) ranging from 14.05% to 17.60%. All compounds are strongly recommended for fabricating efficient OSCs with excellent PV properties. The current work is a step towards environmentally friendly organic PV and will pave the way for future structural engineering research for the efficient material design of OSCs.

Study on the electronic structures and NLO properties of C6H6F6 doped superalkalis X3M (X=Li, na, K; M=O, S, Se)

To explore novel high-performance nonlinear optical (NLO) materials, this paper focuses on studying and discussing the geometric, electrical, and NLO properties of superalkali-doped C6H6F6. Geometrical and thermodynamic properties have been calculated by density-functional theory (DFT) calculations at the ωB97XD/6-31 + G (d,p) level of theory. Electronic properties related to charge transfer between the superalkali and C6H6F6 were obtained through calculations such as NBO charge analysis and frontier molecular orbitals (FMO). The electronic properties are rationalized by the density of states analysis, and in this paper, using the two-energy level model to analyzed the factors that affect the first hyperpolarizability. The frequency-dependent hyperpolarisation coefficients are analyzed to understand the dynamic NLO response. To obtain the NLO response of these new complexes experimentally, the Hyper-Rayleigh scattering (βHRS) coefficients of the complexes were also investigated. The dynamic and static hyperpolarizability properties of these complexes show good NLO response. It is also hoped that this work may provide theoretical help for the future synthesis of new efficient NLO materials.

Effect of tensile deformation on the optoelectronic properties of black phosphine-doped lithium atoms.

First-principles calculations based on the generalized gradient approximation gradient and the Perdew-Burke-Ernzerhof function (GGA-PBE generalized function) are carried out on the intrinsic and lithium-doped black phosphine systems to investigate the effects of different uniaxial tensile deformations on the electronic and optical properties of the systems. It is shown that the structural stability of the intrinsic and lithium-doped systems decreases with increasing tensile deformation, and all systems are most stable at 0% tensile deformation. The intrinsic black phosphazene system is a direct band gap semiconductor, and its band gap increases and then decreases with tensile deformation and reaches a maximum value of 1.086eV at 4%. Lithium doping closes the band gap of the black phosphazene system, which is metallic in nature, but the band gap is opened up when the tensile deformation is 4-6%. From the density of states analysis, the density of states of all systems is basically contributed by the s and p orbitals, with little contribution from the d orbitals, and the contribution from the p orbitals is dominant. From the analysis of optical properties, the increase of tensile deformation causes the absorption peaks of the intrinsic system to redshift then blueshift then redshift, causes the absorption peaks of the lithium-doped system to redshift, and causes the reflection peaks of all systems to redshift. In addition, lithium doping blueshifts the absorption and reflection peaks of the systems compared to the intrinsic black phosphazene system. Using the CASTEP section of the Materials Studio software, first-principle calculations based on density functional theory are done on the top-site doped lithium atoms of monolayer black phosphine under uniaxial stretching deformation in the a-direction, and the generalized gradient approximation gradients and Perdew-Burke-Ernzerhof functions (GGA-PBE generalized functionals) are used for the optimization and approximation process. The optimization parameters are set for the supercell structure: its plane-wave truncation energy is set to 400eV, its Brillouin zone K-point grid is set to 3*3*3, its self-consistent field iteration accuracy convergence value is 2.0e-6eV/atom, the convergence basis of its structural optimization is 0.02eV/ Å, and the convergence of the stress value is 0.05 gpa. During the optimization period, the interaction force between atoms is 0.03eV/ Å and the atomic displacement is less than 0.001Å. To eliminate the effect of interlayer forces, a vacuum layer with a thickness of 15Å is placed in its vertical direction (i.e., c-axis direction).

First-principles study of the electronic and optical properties of Nb-doped MoSe2 by tensile strain

A first-principles method was used to explore the influence of tensile strain on the electrical and optical characteristics of Nb-doped MoSe2. The tensile strain has been discovered to have a higher influence on the electrical structure of the Nb-doped MoSe2 system than pure monolayer MoSe2. According to the energy band structure study, the pure monolayer MoSe2 is a direct bandgap semiconductor, but the system doped with Nb instead of Mo atoms is a p-type-doped semiconductor. The bandgap of the Nb-doped MoSe2 system decreases gradually with the increase of tensile strain, but still maintains the p-type semiconductor properties, and the bandgap of the pure monolayer MoSe2 also decreases gradually with the increase of tensile strain. From the density of states analysis, it is found that for the total density of states of the doped system at different tensile strains, it is mainly contributed by the Mo-4d and Se-4p orbitals. The optical properties analysis showed that the doped system under tensile strain had higher absorption coefficient and reflectance peak than the Nb-doped MoSe2 system without tensile strain. Additionally, the doped system showed redshift phenomenon in both the absorption and reflection peaks as the tensile strain increased.

First-principles study of the effect of oxygen vacancy and iridium doping on formaldehyde adsorption on the La2O3(001) surface.

Formaldehyde adsorption on intrinsic La2O3 surface, four-fold coordinated oxygen vacancy (VO4c), six-fold coordinated oxygen vacancy (VO6c), and iridium-doped La2O3(001) surface was studied by the first-principles method. The results show that formaldehyde adsorption on the Ir-doped La2O3(001) surface with VO6c is the strongest because of the directional movement of electrons caused by the interaction of the Ir-5d orbitals and internal oxygen vacancy, wherein the adsorption energy is 3.23 eV. This model showed a significant increase in adsorption energy, indicating that Ir doping improves the formaldehyde adsorption capacity of the La2O3(001) surface. The energy band analysis shows that iridium doping introduces impurity energy levels into the intrinsic La2O3 energy band, which enhances the interaction between the La2O3(001) surface and formaldehyde molecules. Density of state analysis indicated that the adsorption of formaldehyde molecules on the La2O3(001) surface is mainly due to the interaction between the O-2p, C-2p orbitals of formaldehyde and the Ir-5d orbital of iridium atoms. Furthermore, the existence of VO4c and VO6c defects has no effect on the position and shape of the valence and conduction bands. The effects of oxygen vacancy and iridium doping on the optical properties mainly appeared in the low-energy infrared and visible regions, making the O-2p, C-2p orbitals of formaldehyde and the Ir-5d, O-2p orbitals of the La2O3(001) surface become hybridized near the Fermi level and the electronic transition from the valence band to conduction band more likely to occur. The La2O3 material can be used as an ideal photocatalytic material for formaldehyde degradation.

Photocatalytic water splitting properties of GeC/InS van der Waals heterostructure: first-principles calculations

Based on first-principles, we conducted an in-depth study of the GeC/InS van der Waals heterostructure formed by GeC and InS and discussed its structure, electronic properties and optical properties. First, we observe that this heterostructure has negative binding energy, indicating that the interlayer interactions are mainly affected by van der Waals forces. Through band structure and density of state analysis, we confirmed its type-II band alignment characteristics, which means that photogenerated carriers have the ability to automatically separate in space. Moreover, the average charge density difference and Bader charge analysis show that there is a built-in electric field in the heterostructure, and further proves that GeC/InS forms a Z-scheme charge transfer mechanism. Interestingly, the band edge position spans the water redox potential and can fully induce the redox reaction of water splitting, indicating that it is a potential photocatalyst. The high light absorption coefficient shown in the absorption spectrum also further confirms its excellent photocatalytic activity. The most striking thing is that the solar hydrogen production efficiency of GeC/InS heterostructure is as high as 44.39%. Our research demonstrates the theoretical basis for GeC/InS heterostructure as a photocatalyst.

Structural, Elastic, Electronic, and Magnetic Properties of Nd‐Doped NaScGe Half‐Heusler Compound by Ab‐Initio Method

AbstractA comprehensive investigation is conducted on the electronic structure and magnetic properties of half‐Heusler NaScGe, which is doped with a rare earth element Nd with different concentrations. The Heusler Na1‐xNdxScGe (where x = 0, 0.25, 0.75, and 1) compounds are thoroughly investigated. The examination encompassed structural, elastic, magnetic, and electronic characteristics using the full potential linearized augmented plane wave (FP‐LAPW) method. Generalized gradient approximation (GGA) is used to calculate the structural parameters and electronic characteristics. The equilibrium lattice constant and band gap of half‐Heusler NaScGe are found to be in good accord with other data. The density of states (DOS) investigation has revealed a semiconductor behavior of half‐Heusler NaScGe and half‐metallic ferromagnetic properties of quaternary‐Heusler Na0.75Nd0.25ScGe, characterized by a moderate band gap in minority spin channel. In addition, the DOS analysis has shown that both ternary half‐Heusler NdScGe and QH Na0.25Nd0.75ScGe compounds have exhibited metallic ferromagnetic activity. The work has introduced a novel approach for producing half metals from the semiconductor half‐Heusler NaScGe. Quaternary‐Heusler Na0.75Nd0.25ScGe is identified as a promising material for applications spintronic.

Insights into structural, electronic, optical properties, and impedance spectroscopy of semi-doped perovskite Nd0.5Ba0.5CoO3: A theoretical and experimental study

In this study, the electronic, structural, and optical properties of semi-doped perovskite Nd0.5Ba0.5CoO3 (NBCO) were investigate using the CASTEP software, which relies on density functional theory (DFT) along with the correlation function of generalized gradient approximation (GGA) and Perdew-Burke-Ernzerhof (PBE). The mesh parameters of the (super) cell indicate that NBCO adopts an orthorhombic structure in the Pmmm space group, featuring a Coulomb Energy (EC) of approximately −244 eV. DFT and total density of states (DOS) analyses reveal that the as-prepared perovskite manifests metallic characteristics, and a notable covalent interaction is observed between the O-p and Co-d spin states, indicating strong hybridization between these orbitals. Remarkably, NBCO demonstrates 100 % spin polarization (P) at the Fermi level, with a calculated total magnetic moment of approximately 3.44 μB. Moreover, low dielectric loss (tgδ) values suggest facile electron movement, and impedance spectroscopy illustrates a dielectric relaxation phenomenon. DFT calculations predict an orthorhombic crystal structure with higher electron density at cobalt atom positions. Band structure and DOS analyses affirm metallic behavior owing to the robust hybridization between oxygen-p and cobalt-d orbitals. Optical property assessments reveal potential applications in spintronics and optoelectronics, with notable absorption in the ultraviolet–visible range. The conductivity spectra from impedance spectroscopy contribute to understanding temperature-dependent charge transport mechanisms. Dielectric constants decrease with increasing frequency and temperature, while dielectric losses remain low, indicating efficient electron movement. The material adheres to a metallic conduction mechanism as described by Drude's law, and the material's 100 % spin polarization at the Fermi level and a total magnetic moment of 3.44 μB are significant findings. Negative dielectric constants observed at specific frequencies suggest potential applications in metamaterials. Overall, the determined properties position NBCO cobaltite as a promising candidate for high-frequency devices, spintronic components, and sensors.

End-capped engineering of carbazole based dopant free hole transporting material with improved power conversion efficiency

Perovskite solar cells (PSCs) belonging to third-generation of solar cells are reported to have better power conversion efficiency, cost-effectiveness, and many other benefits. This computational investigation focuses on designing five indolo(3,2-b) carbazole (ICZ) central core containing small hole transport materials (HTMs) to discover photovoltaic properties as donors for perovskite solar cells accompanied by enhanced charge mobility. New HTMs with A–π–D–π–A skeleton has been designed by thiophene-bridged end-capped acceptor engineering on reference molecule (ICZ-R). Absorption spectra, frontier MOs, density of state analysis, molecular electrostatic potential surfaces, transition density matrix, non-covalent interactions, iso-surface maps, and planarity parameters were analyzed through different softwares for better-predicting performance of perovskite solar cells. All tailored HTMs showed better absorption profiles. Among them, ICZ-D3 exhibited the maximum absorbance λmax at 695 nm in dichloromethane solvent and the greatest full-width half maximum (313.93 nm). ICZ-D2 showed the lowest Eg of 1.62 eV, and the highest dipole moment (8.35 D) in the solvent phase, showing admirable solubility. Designed HTMs exhibited decelerated HOMO values (−4.62 to −5.25), lower values of binding energies (0.0323–0.388 <0.542 eV), better intrinsic charge transfer percentage (10.74–72.71%>7.88), lower hardness (0.81–1.11 <1.78 eV) and greater softness values (0.90–1.23 >0.56 eV) as compared to ICZ-R. All designed HTMs demonstrated higher estimated VOC and power conversion efficiency (PCE=11.81–25.90%) than ICZ-R, leading to fruitful applications. ICZ-D4 resulted in the highest PCE (25.90%) with better VOC (1.25 eV). These outstanding findings paved a new way to develop better-performing HTMs for PSCs.

Density functional theory studies of Ti3C2T x MXene nanosheets decorated with Au for sensing SF6/N2 nitrogen-containing decomposition gases

SF6/N2 mixture is an alternative gas of SF6, which is already used in electrical equipment. When a malfunction occurs , SF6/N2 will decompose and further react with trace water and oxygen to produce nitrogen-containing gases such as NO, NO2, N2O and NF3. It is necessary to monitor these gases to ensure the safe operation of the equipment. This paper is based on density functional theory (DFT), the nanomaterial Ti3C2T x doped with Au atom was selected as sensing material. The result shows that Au/Ti3C2T x has larger adsorption energy when NO and NO2 adsorbed on the surface, the stable structures were conformed more easily with NO and NO2 compared with N2O and NF3. The density of states analysis and the frontier molecule orbital analysis reveal more change of the system before and after NO and NO2 adsorption, suggesting the material showed good sensitivity performance to NO and NO2. Thus, Au/Ti3C2T x is considered to have the potential for sensing NO and NO2.

Enhancement of nonlinear optical properties of nanocarbon cluster C60 by aluminum doping

AbstractThe search for good nonlinear optical (NLO) materials is of utmost importance in laser technology and optical information science, making it a popular research topic in materials science. It is reported that the introduction of alkali metal Li can enhance the NLO properties of nanocarbon materials. Here, metal Al, which exhibits similar electron transfer characteristics to Li, was used for the first time to enhance the NLO properties of nanocarbon cluster C60, which possesses a large delocalized π structure and the highest yield in the fullerene family. Density functional theory calculations in combination with Boltzmann distribution showed that the most thermodynamically stable Al@Ih(1812)‐C60 exhibited good second‐order NLO properties, which originated from the noncentrosymmetry geometry and one extra delocalized electron on Ih(1812)‐C60 from the 3p shell of inner Al. Density of state analysis indicated that the molecular orbitals of Al@Ih(1812)‐C60 were primarily formed by Ih(1812)‐C60 with minimal Al participation, and the presence of Al always resulted in an antibonding orbital effect. Bond critical point and electron localization function analyses indicated almost no covalent interaction between Al and Ih(1812)‐C60. Exohedral functionalization was employed to further stabilize Al@Ih(1812)‐C60 with radical character, and the infrared spectrum was also analyzed in detail. This study has promising implications for expanding the potential applications of fullerenes in optical devices.

Electronic and optical properties of chemically modified 2D GaAs nanoribbons

We employed density functional theory calculations to investigate the electronic and optical characteristics of finite GaAs nanoribbons (NRs). Our study encompasses chemical alterations including doping, functionalization, and complete passivation, aimed at tailoring NR properties. The structural stability of these NRs was affirmed by detecting real vibrational frequencies in infrared spectra, indicating dynamical stability. Positive binding energies further corroborated the robust formation of NRs. Analysis of doped GaAs nanoribbons revealed a diverse range of energy gaps (approximately 2.672 to 5.132 eV). The introduction of F atoms through passivation extended the gap to 5.132 eV, while Cu atoms introduced via edge doping reduced it to 2.672 eV. A density of states analysis indicated that As atom orbitals primarily contributed to occupied molecular orbitals, while Ga atom orbitals significantly influenced unoccupied states. This suggested As atoms as electron donors and Ga atoms as electron acceptors in potential interactions. We investigated excited-state electron–hole interactions through various indices, including electron–hole overlap and charge-transfer length. These insights enriched our understanding of these interactions. Notably, UV–Vis absorption spectra exhibited intriguing phenomena. Doping with Te, Cu, W, and Mo induced redshifts, while functionalization induced red/blue shifts in GaAs-34NR spectra. Passivation, functionalization, and doping collectively enhanced electrical conductivity, highlighting the potential for improving material properties. Among the compounds studied, GaAs-34NR-edg-Cu demonstrated the highest electrical conductivity, while GaAs-34NR displayed the lowest. In summary, our comprehensive investigation offers valuable insights into customizing GaAs nanoribbon characteristics, with promising implications for nanoelectronics and optoelectronics applications.

Improving hydrogen evolution catalytic activity of 2D carbon allotrope biphenylene with B, N, P doping: Density functional theory investigations

Using a first principles approach, we studied the hydrogen evolution reaction activity of newly synthesized biphenylene and B, N, P decorated biphenylene sheet. Hydrogen evolution reaction activity of pristine biphenylene sheet is not encouraging, as it is similar to pristine graphene. The Gibbs free energy and overpotential of P(N) doped on biphenylene sheet are 0.022 (−0.092) eV and 22 (92) mV, respectively. The reported Gibbs free energy and overpotential of Pt are 0.9 eV and 90 mV. Hence doping of P(N) atom on top of biphenylene sheet improves hydrogen evolution reaction activity much better (near to) Pt metal. We analyzed the adsorption mechanism of dopants (B, N, P) and hydrogen with Bader charge analysis and density of states analysis. P and N-decoration on biphenylene sheet change its electronic structure so that one obtains improved hydrogen evolution reaction activity for P and N-doped biphenylene sheet. Furthermore, the stability of N, P decorated biphenylene at room temperature with ab-initio molecular dynamics and formation energy near that of biphenylene indicate experimental feasibility. We have compared all our best hydrogen evolution reaction activity results in the reaction coordinate and volcano plots of pristine, B, N, and P-doped BPh sheets. They indicate that P-doped biphenylene is a metal-free, powerful catalyst for hydrogen evolution reaction activities.

Designing of banana shaped chromophores via molecular engineering of terminal groups to probe photovoltaic behavior of organic solar cell materials

To meet the rising requirement of photovoltaic compounds for modernized hi-tech purpose, we designed six new molecules (DTPD1-DTPD6) from banana shaped small fullerene free chromophore (DTPR) by structural tailoring at terminal acceptors. Frontier molecular orbitals (FMOs), density of states (DOS), open circuit voltage (Voc), transition density matrix (TDM) analysis, optical properties, reorganization energy value of hole and electron were determined utilizing density function theory (DFT) and time-dependent density function theory (TD-DFT) approaches, to analyze photovoltaic properties of said compounds. Band gap contraction (∆E = 2.717–2.167 eV) accompanied by larger bathochromic shift (λmax = 585.490–709.693 nm) was observed in derivatives contrary to DTPR. The FMOs, DOS and TDMs investigations explored that central acceptor moiety played significant role for charge transformation. The minimum binding energy values for DTPD1-DTPD6 demonstrated the higher exciton dissociation rate with greater charge transferal rate than DTPR, which was further endorsed by TDM and DOS analyses. A comparable Voc (1.49–2.535 V) with respect to the HOMOPBDBT–LUMOacceptor for entitled compounds was investigated. In a nutshell, all the tailored chromophores can be considered as highly efficient compounds for promising OSCs with a good Voc response.