Department of Physics
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Item Investigating the stable structures of yttrium oxide clusters: Yn clusters as promising candidates for O2 dissociation†(RSC, 2025-03) Bandyopadhyay, DebashisThis study presents threshold photoionization (PI) spectra for a series of yttrium oxide clusters (YnOm, n = 2–8, m = 2–4) in the photon energy range of 192 to 300 nm (6.46 to 4.13 eV). Density functional theory (DFT) is employed to explore the stable structures of these clusters. For YnO2 clusters, experimental PI spectra are compared with calculated spectra for the lowest-energy and near-lowest-energy structural isomers. Stable structures contributing to the experimental PI spectra are identified. Experimentally corrected adiabatic ionization energies for YmO2 clusters are determined. The newly identified lowest-energy structure for Y2O2 differs from those in previous literature studies, while larger clusters show better agreement, primarily varying in oxygen binding sites. Molecular oxygen-absorbed configurations of yttrium oxide clusters are generally unstable or energetically unfavorable, with O2 activation occurring via charge transfer from yttrium to oxygen. Climbing image nudged elastic band (CI-NEB) calculations indicate that YnO2 forms in the ground state when an O2 molecule is absorbed onto low- or under-coordinated sites such as corners or edges of Yn clusters. This process involves the dissociation of the O–O bond, followed by the adsorption of individual O atoms at different sites on the Yn clusters. Analysis of the total density of states (TDOS) and partial density of states (PDOS) reveals an increased orbital density near the Fermi level, indicating a strong reaction affinity between Y and O atoms.Item A Novel 2D-hBNX covalent inorganic framework functionalized with transition metals for enhanced catechol sensing: A density functional investigation(Elsevier, 2025-06) Bandyopadhyay, DebashisCovalent inorganic frameworks (IOFs) with tunable porosity and structural versatility have emerged as promising platforms for environmental contaminant detection. This study employs density functional theory (DFT) to investigate a novel transition metal (TM = Ni, Pd, Pt)-functionalized hexaboronitroxene (hBNX: B9O3N9H6) as a 2D IOF-based sensor for the detection of catechol (CC), a hazardous environmental pollutant. TM doping significantly modifies the electronic properties of hBNX, as revealed by band structure and density-of-states analyses, enhancing CC adsorption and sensitivity. While pristine hBNX weakly interacts with CC (-0.76 eV), Ni (-1.26 eV) and Pt (-1.11 eV) improve adsorption, whereas Pd (-0.72 eV) weakens it. Optical property variations further support these findings. Structural stability assessments via ab initio molecular dynamics and phonon analyses confirm the thermal resilience of Pt.hBNX up to 350 K. The sensor exhibits exceptional sensitivity (1.28 × 10⁸) and facilitates CC desorption under realistic environmental conditions—requiring 93 s under visible light at 400 K and 1.77 s under UV light at 350 K. Additionally, a high diffusion energy barrier (3.58 eV) ensures strong TM anchoring, enhancing sensor durability. These findings establish TM-functionalized 2D hBNX as a highly stable and efficient material for hazardous pollutant detection, contributing to advanced environmental monitoring technologiesItem Insights into the reversible hydrogen storage mechanism of transition metal-decorated Irida-graphene: a DFT study(Elsevier, 2025-06) Bandyopadhyay, DebashisAddressing the challenges of fuel energy requires identifying potential materials that offer high hydrogen storage ability and stability at ambient conditions, along with optimal desorption temperatures. The present study investigates TM-doped (TM = Sc, Ti, V and Nb) 2D Irida-Graphene (IG), as the possibility of potential hydrogen storage material through first-principles calculations. Among the triangular, hexagonal and octagonal carbon rings of Irida-Graphene, the TM atoms strongly bond to the hexagonal rings. It is found that 1TM can adsorb a maximum of 16H2 molecules, resulting in an average adsorption energy ranging from −0.714 (1Nb.8H2) to −0.150 (2Ti.32H2) eV/H2 and a gravimetric density ranging from 3.391 wt% (1Nb.4H2) to 21.61 wt% (2Sc.32H2). High diffusion energy barriers of 7.14 eV (Sc.IG), 7.32 eV (Ti.IG) and 7.08 eV (V.IG) prevents the clustering of TM-TM atoms. Ab-initio molecular dynamics and phonon dynamics simulations indicate stability at 450 K, above the temperature at which desorption occurs.Item Unveiling reversible hydrogen storage mechanism on transition metal decorated 2D holey graphyne: a density functional study(Elsevier, 2025-07) Bandyopadhyay, DebashisThis study investigates hydrogen adsorption and storage in pristine and transition metal (TM = V, Nb, Cr) doped 2D graphene allotrope, Holey Graphyne (HGY), using density functional theory. The TM-decorated HGY systems demonstrate impressive hydrogen storage capacities, with each TM atom capable of binding up to 16H2 molecules. The gravimetric densities for vanadium, chromium, and niobium doping are 14.09 wt%, 14.02 wt%, and 11.93 wt%, respectively, all meeting U.S. Department of Energy standards. Adsorption energies range from −0.17 eV to −0.58 eV per H2 molecule for n = 4 to 32, with calculated desorption temperatures of 326 K, 273 K, and 386 K for 2V.HGY.32H2, 2Cr.HGY.32H2, and 2Nb.HGY.32H2, indicating practical suitability for hydrogen storage. Molecular dynamics and NEB calculations confirm structural stability and sufficient diffusion barriers to prevent metal clustering. Overall, TM-doped HGY emerges as a promising candidate for advanced hydrogen storage, paving the way for innovative energy solutions.Item Investigating the structural, electronic, and magnetic properties of Fe2@Genα (α = 0, +1, −1, n = 1–13) nanoclusters: DFT insights(Elsevier, 2025-10) Bandyopadhyay, DebashisIn this study, we perform a comprehensive investigation of charged iron-germanium nanoclusters, denoted as Fe2Genα (α = 0, ±1; n = 1–13), using density functional theory (DFT). Our primary focus lies in understanding their structural, electronic, and magnetic characteristics. The results reveal a progressive increase in binding energy with cluster size, indicating enhanced stability as the cluster size increases. Notably, Fe2Ge10 and Fe2Ge12 exhibit exceptional thermodynamic stability, suggesting “magic number” behavior for these specific compositions. The highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) gap systematically narrows with increasing cluster size, ranging between 1.5 and 2.5 eV for both neutral and anionic clusters, which points to tunable electronic properties. Structural analysis indicates that the incorporation of Fe atoms into germanium-based cage-like frameworks significantly enhances the overall stability of the clusters. Moreover, charge transfer from Fe to surrounding Ge atoms plays a critical role in modulating both electron distribution and magnetic behavior. Most clusters exhibit a total magnetic moment of approximately 6 μB, with the notable exception of Fe2Ge9, which displays a reduced moment of 4 μB. These insights into the structure–property relationships of Fe–Ge nanoclusters highlight their promise for applications in nanotechnology, particularly in the rational design of functional cluster-based materials.Item Ammonia activation and nitride formation pathways in transition metal clusters: insights from mass spectrometry and first-principles DFT(ACS, 2025-08) Bandyopadhyay, DebashisThe interaction of ammonia (NH3) with laser-vaporized transition metal clusters (Ti, V, Fe, Co, and Ni) was systematically investigated using reflectron time-of-flight mass spectrometry and density functional theory. Metal-specific and size-dependent trends emerge: Ti clusters readily form (TiN)n (n = 1–7), indicating strong nitride formation. Neutral Vn and Fen clusters predominantly yield mononitrides, with the NH3 dehydrogenation efficiency varying with cluster size and charge. Con clusters show limited reactivity with mainly NH3 adsorptions and partial dehydrogenation, while Nin clusters exhibit extensive NH3 uptake, leading to stable nitride/imide species such as NiN(NH3)4 and Ni(NH)2(NH3)4, along with the formation of Ni+H2 via hydrogen release─likely resulting from the reaction of Nin+ clusters with NH3. These findings provide insights into ammonia activation, N–H bond cleavage, and transition metal nitride formation mechanisms in small clusters.Item First-principles study of transition metal doped in 2d polyaramid for novel material modelling(2025-10) Bandyopadhyay, DebashisWe present a first--principles density functional theory (DFT) study of transition metal (TM = Ti, Cr, Mn, Fe, Co, Ni) functionalized two--dimensional polyaramid (2DPA) to explore their structural, electronic, and magnetic properties. Mechanical parameters, such as bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and Pugh ratio, together with phonon dispersion, confirm the mechanical and dynamic stability of all doped systems. Electronic structure analysis shows strong binding of Co, Cr, Fe, Ni, and Ti with formation energies between --1.15 eV and --2.96 eV, while Mn binds more weakly (--0.67 eV). TM doping introduces new electronic states that reduce the band gap, with Fe-doped 2DPA exhibiting the lowest value of 0.26 eV. The systems display predominantly ferromagnetic ordering, with magnetic moments of 1.14 {\mu}B (Co), 3.57 {\mu}B (Cr), 2.26 {\mu}B (Fe), 4.19 {\mu}B (Mn), and 1.62 {\mu}B (Ti). These results demonstrate that TM--doped 2DPA possesses tunable magnetic and electronic characteristics, highlighting its potential for spintronic applications.Item Boron nitride nanotubes as efficient surface absorbers for air pollutant gas molecules: insights from density functional theory(2025-11) Bandyopadhyay, DebashisThis study investigates into the adsorption sensing capabilities of single-walled (5,5) boron nitride nanotubes (BNNTs) towards environmental pollutant gas molecules, including CH2, SO2, NH3, H2Se, CO2 and CS2. Employing a linear combination of atomic orbital density functional theory (DFT) and spin-polarized generalized gradient approximation (GGA), the investigation reveals the nanotube's robust adsorption behavior without compromising its structural integrity. Thermodynamic and chemical parameters, such as adsorption energy, HOMO-LUMO gap, vertical ionization energy, and vertical electron affinity, highlight the (5,5) BNNTs' potential as efficient absorbents for pollutant molecules. Infrared spectroscopy confirms the formation of distinct BNNT-gas complexes. These findings underscore the promising application of BN nanotubes as absorbents for common gaseous pollutants, essential for developing sensors to enhance indoor air quality.Item Elastic and strain--tunable electronic and optical properties of la2algao6 hybrid perovskite: a first-principles study(2025-11) Bandyopadhyay, DebashisPerovskite materials, known for their structural versatility and multifunctional properties, continue to draw interest for advanced electronic and optoelectronic applications. In this study, we investigate the elastic and strain--engineered mechanical, electronic properties and optical properties of the orthorhombic La2AlGaO6 (LAGO) hybrid perovskite using first--principles quantum mechanical calculations based on density functional theory (DFT). Structural optimizations were performed using both the local density approximation (LDA) and the generalized gradient approximation (GGA). The mechanical stability of LAGO was confirmed through the Born--Huang criteria, and key elastic constants (C11, C12, C33, C44, and C66) were evaluated. These constants were further used to derive mechanical parameters such as Young's modulus, bulk modulus, shear modulus, Poisson's ratio, Cauchy's pressure, and anisotropic factor, offering insights into the material's ductility, hardness, and elastic anisotropy. Crucially, we explored the influence of biaxial strain on the electronic band structure, DOS/PDOS, and Fermi energy, revealing significant band gap modulation under compressive and tensile strain, and hence, varying the optical properties. The coupling between elastic response and electronic structure highlights LAGO's potential for tunable device applications, where mechanical stimuli can be employed to tailor its electronic functionality.Item Unveiling the adsorption and electronic interactions of drugs on 2D graphsene: insights from dft and machine learning approach(2025-11) Bandyopadhyay, DebashisEfficient identification of promising drug candidates for nanomaterial-based delivery systems is essential for advancing next-generation therapeutics. In this work, we present a synergistic framework combining density functional theory (DFT) and machine learning (ML) to explore the adsorption behavior and electronic interactions of drugs on a novel 2D graphene allotrope, termed Graphsene (GrS). Graphsene, characterized by its porous ring topology and large surface area, offers an excellent platform for efficient adsorption and strong electronic coupling with drug molecules. A dataset comprising 67 drugs adsorbed on various 2D substrates was employed to train the ML model, which was subsequently applied to predict suitable drug candidates for GrS based on molecular size and adsorption energy criteria (database link provided in a later section). The ML model exhibited robust predictive accuracy, achieving a mean absolute error of 0.075 eV upon DFT validation, though its sensitivity to initialization highlighted the need for larger and more diverse datasets. DFT-based analyses, including adsorption energetics, projected density of states (PDOS), and Bader charge calculations, revealed pronounced charge transfer and electronic coupling between the drug molecules and the GrS surface, elucidating the fundamental nature of drug-substrate interactions. The study reveals that the integrated DFT-ML strategy offers a rapid, cost-efficient approach for screening and understanding drug-nanomaterial interactions, paving the way for data-driven design of advanced nanomaterial-enabled drug delivery systems.