International Journal of Physics

International Journal of Physics | Vol. 14, No. 12, December 2023 | pp. 89–96

DOI: 10.46882/2023/IJP/000164

Research Article

Title: Density Functional Theory Analysis of Catalytic Oxygen Transformation on Nitrogen-Doped Carbon Nanoribbons

Names of Authors: A. L. Silva¹, H. L. Mueller²

Authors’ Affiliations:
¹ Institute of Physics, Federal University of Rio Grande do Sul, Porto Alegre, Brazil
² Institut für Kernphysik, Karlsruher Institut für Technologie, Karlsruhe, Germany

Abstract: The electrochemical oxygen evolution reaction (OER) is essential for chemical solar energy conversion networks and modern water-splitting setups. This investigation uses density functional theory calculations to analyze the catalytic performance and reaction mechanisms of oxygen transformation on nitrogen-doped carbon nanoribbons. We modeled three distinct configurations: edge pyridinic, center pyrrolic, and quaternary nitrogen doping patterns. Free energy profiles for intermediate steps leading to molecular oxygen (*OH, *O, and *OOH) were computed using the computational hydrogen electrode framework. The calculations demonstrate that edge pyridinic nitrogen sites lower the activation barrier for the rate-determining step (*O -> *OOH) to 0.48 eV. This value is significantly lower than the 1.25 eV barrier calculated for pristine carbon surfaces. The overpotential required to trigger selective oxygen evolution on pyridinic configurations was estimated at -0.42 V versus the standard hydrogen electrode. Charge density difference mappings show that nitrogen doping induces localized spin polarization and electron deficiency on adjacent carbon atoms. This electronic reconfiguration stabilizes the adsorbed intermediates. These quantum mechanical insights provide theoretical guidelines for developing metal-free, carbon-based catalysts for efficient solar fuel production plants.

Keywords: Oxygen evolution reaction; density functional theory; nitrogen-doped carbon; electrocatalysis; reaction mechanism; overpotential

Manuscript Timeline: Received: September 15, 2023; Revised: October 30, 2023; Accepted: November 15, 2023; Published: December 15, 2023

Citation: Silva, A. L., & Mueller, H. L. (2023). Density Functional Theory Analysis of Catalytic Oxygen Transformation on Nitrogen-Doped Carbon Nanoribbons. International Journal of Physics, 14(12), 89–96.

International Journal of Physics | Vol. 14, No. 11, November 2023 | pp. 81–88

DOI: 10.46882/2023/IJP/000163

Research Article

Title: Finite Element Modeling of Acoustic Wave Focusing and Tunability in Porous Piezoceramic Acoustic Lenses

Names of Authors: P. J. O’Connor¹, V. I. Morozov²

Authors’ Affiliations:
¹ Department of Civil and Environmental Engineering, University College Cork, Cork, Ireland
² Institute of High Pressure Physics, Russian Academy of Sciences, Troitsk, Russia

Abstract: Controlling acoustic wave transmission paths and focal spots in fluid-saturated structural arrays is essential for developing non-destructive evaluation systems, ultrasound medical diagnostics, and underwater sonar grids. This study presents a finite element modeling approach to simulate acoustic wave scattering and track focus tuning profiles within a gradient-index porous piezoceramic metamaterial matrix. The mathematical model integrates Biot's dynamic equations of poroelasticity with a generalized piezoelectric constitutive framework to account for electro-mechanical coupling under variable external electrical shunting networks. Numerical simulations were executed across an ultrasonic frequency spectrum from 20.0 kHz to 600.0 kHz. The computational results demonstrate that introducing active inductive-capacitive shunts induces a strong, tunable focus alteration for the fast compressional wave mode at 210.0 kHz. This localized spot can be actively shifted by 35.0% across the spatial domain via external load tuning. The scattering cross-section displays a non-linear dependence on core porosity fractions, showing optimal bandgap breadth below a 22.0% threshold. Experimental validation was conducted using synthetic barium titanate porous specimens filled with matching viscoelastic liners, matching the numerical attenuation data within a ±5.5% margin.

Keywords: Acoustic metamaterials; piezoceramics; finite element modeling; Biot's theory; focus tuning; porous media

Manuscript Timeline: Received: August 18, 2023; Revised: October 10, 2023; Accepted: November 02, 2023; Published: November 14, 2023

Citation: O’Connor, P. J., & Morozov, V. I. (2023). Finite Element Modeling of Acoustic Wave Focusing and Tunability in Porous Piezoceramic Acoustic Lenses. International Journal of Physics, 14(11), 81–88.

International Journal of Physics | Vol. 14, No. 10, October 2023 | pp. 73–80

DOI: 10.46882/2023/IJP/000162

Research Article

Title: Fluid Velocity Mapping and Energy Transmutation Profiles in Solar Corona Active Regions

Names of Authors: G. R. Davies¹, A. M. El-Chemali²

Authors’ Affiliations:
¹ School of Physics and Astronomy, University of St Andrews, St Andrews, UK
² Department of Physics, Faculty of Science, Lebanese University, Beirut, Lebanon

Abstract: Magnetic reconnection is the primary physical process driving explosive energy releases in solar atmospheric plasma, heating material to millions of Kelvin and accelerating the fast solar wind. This paper evaluates fluid velocity mapping and quantifies local magnetic reconnection rates within an active solar corona coronal loop interaction. We utilized high-resolution spectroscopic data from space-based extreme ultraviolet (EUV) channels tracking highly ionized iron lines (Fe XII and Fe XV). Differential affine velocity estimator algorithms were deployed to construct two-dimensional velocity fields of plasma inflows and outflows surrounding the current sheet layer. The empirical measurements reveal systematic plasma inflows moving at 20.5 km/s, while directed outflows reach velocities of 340.0 km/s along the magnetic boundary corridors. Based on these transport metrics, the local dimensionless reconnection rate was calculated to range between 0.06 and 0.09. These values closely match fast reconnection regimes predicted by the Petschek theoretical framework modified by localized turbulent transport. Spectroscopic line-broadening analysis indicates localized turbulent temperatures peaking at 8.8 MK within the diffusion region, confirming intense localized viscous dissipation fields. These imaging diagnostics provide direct observational parameters for refining magnetohydrodynamic models of solar wind acceleration loops.

Keywords: Solar corona; magnetic reconnection; extreme ultraviolet; plasma velocity; solar flares; magnetohydrodynamics

Manuscript Timeline: Received: July 12, 2023; Revised: September 04, 2023; Accepted: September 22, 2023; Published: October 10, 2023

Citation: Davies, G. R., & El-Chemali, A. M. (2023). Fluid Velocity Mapping and Energy Transmutation Profiles in Solar Corona Active Regions. International Journal of Physics, 14(10), 73–80.

International Journal of Physics | Vol. 14, No. 9, September 2023 | pp. 65–72

DOI: 10.46882/2023/IJP/000161

Research Article

Title: Optical Properties and Polariton Confinement of Monolayer Molybdenum Disulfide on Silicon Nitride Microdisks

Names of Authors: Y. S. Kim¹, T. H. Nguyen²

Authors’ Affiliations:
¹ Department of Physics and Astronomy, Seoul National University, Seoul, South Korea
² Department of Physics, Vietnam National University, Hanoi, Vietnam

Abstract: Monolayer transition metal dichalcogenides have attracted significant interest due to their strong light-matter interactions and potential for integrated nanophotonic circuits. This study characterises the optical properties and exciton-polariton dynamics of monolayer molybdenum disulfide (MoS²) integrated onto silicon nitride microdisk resonators. The monolayer flakes were synthesized via chemical vapor deposition and transferred onto the waveguides using an optimized dry-transfer technique. We performed micro-photoluminescence and angle-resolved reflectivity measurements under mechanical tensile strains from 0.0% to 1.6% at a room temperature of 300 K. The unstrained monolayer coupled to the evanescent field of the microdisk exhibits strong absorption lines, confirming efficient whispering-gallery mode phase-coupling. Applying a 1.0% tensile strain shifts the exciton resonance energy from 1.85 eV to 1.79 eV, yielding a strain tuning factor of 60.0 meV/% strain. Time-resolved photoluminescence spectroscopy revealed a shortened polariton decay lifetime, dropping from 16.5 ps down to 5.2 ps due to the cavity Purcell effect. Our numerical models confirm that the localized electromagnetic field confinement within the core increases the exciton-photon coupling rate by 35.0%. These findings demonstrate that cavity-integrated strain engineering offers an effective route for controlling polaritonic states.

Keywords: Molybdenum disulfide; silicon nitride; photoluminescence; exciton dynamics; whispering-gallery modes; integrated photonics

Manuscript Timeline: Received: June 04, 2023; Revised: July 28, 2023; Accepted: August 18, 2023; Published: September 11, 2023

Citation: Kim, Y. S., & Nguyen, T. H. (2023). Optical Properties and Polariton Confinement of Monolayer Molybdenum Disulfide on Silicon Nitride Microdisks. International Journal of Physics, 14(9), 65–72.

International Journal of Physics | Vol. 14, No. 8, August 2023 | pp. 57–64

DOI: 10.46882/2023/IJP/000160

Research Article

Title: Optical Soliton Perturbations and Wave Collapse Dynamics in Non-Local Graphene-Oxide Lattices

Names of Authors: S. H. Zhang¹, Y. S. Kim²

Authors’ Affiliations:
¹ Department of Physics, Tsinghua University, Beijing, China
² Department of Physics and Astronomy, Seoul National University, Seoul, South Korea

Abstract: Designing non-linear optical configurations that can stabilize ultra-short pulse propagation or safely arrest high-power beam collapse is an essential goal for laser engineering and high-speed communications. This paper solves the generalized non-linear Schrödinger equation governing optical soliton perturbations and tracks wave collapse dynamics inside non-local graphene-oxide lattices. The mathematical model integrates higher-order perturbation terms, including third-order dispersion, self-steepening, and delayed Raman response steps. We applied the inverse scattering transform method combined with a multiple-scale perturbation routine to derive analytical solutions for stable single-solitons and breathers. The results demonstrate that a high degree of spatial non-locality effectively suppresses catastrophic self-focusing collapse, stabilizing two-dimensional structures that are unstable in local Kerr devices. The modulation instability growth rate was calculated against variable perturbation frequencies, highlighting a maximum gain coefficient of g = 2.76 cm⁻¹ under an input beam intensity of 1.6 kW/cm². Expanding the non-locality parameter from 0.6 mm to 3.5 mm reduces the peak instability gain by 64.0% and shifts the peak gain toward longer perturbation wavelengths, avoiding pulse fragmentation.

Keywords: Nonlinear optics; spatial solitons; nonlinear Schrödinger equation; modulational instability; non-local media; wave collapse

Manuscript Timeline: Received: May 12, 2023; Revised: July 03, 2023; Accepted: July 25, 2023; Published: August 14, 2023

Citation: Zhang, S. H., & Kim, Y. S. (2023). Optical Soliton Perturbations and Wave Collapse Dynamics in Non-Local Graphene-Oxide Lattices. International Journal of Physics, 14(8), 57–64.

International Journal of Physics | Vol. 14, No. 7, July 2023 | pp. 49–56

DOI: 10.46882/2023/IJP/000159

Research Article

Title: Superconducting Gap Profiles and Interband Spin Fluctuations in Electron-Doped Pnictide SrFe2As2 Single Crystals

Names of Authors: I. R. Sokolov¹, V. I. Morozov²

Authors’ Affiliations:
¹ Kapitza Institute for Physical Problems, Russian Academy of Sciences, Moscow, Russia
² Institute of High Pressure Physics, Russian Academy of Sciences, Troitsk, Russia

Abstract: Establishing the exact pairing symmetries of iron-based pnictide superconductors remains a primary challenge within modern solid-state and condensed matter physics pipelines. We synthesized high-quality single crystals of electron-doped SrFe2As2 using a specialized self-flux crystal growth routine under pressure parameters. The internal superconducting gap profiles and spin fluctuations were evaluated using high-resolution angle-resolved photoemission spectroscopy and low-temperature London penetration depth tracking. The single crystals displayed a sharp superconducting transition at Tc = 26.0 K with an exceptionally narrow magnetic susceptibility transition width of ΔT = 0.3 K. The temperature dependence of the London penetration depth exhibits an exponential profile at low operational targets (T less than 0.3 Tc), ruling out the existence of line nodes across the order parameter. The photoemission mapping revealed two distinct, fully gapped isotropic superconducting bands across the Fermi surface. The large gap magnitude was measured at Δ1 = 7.1 meV on the inner hole-like sheet, while the lower gap registered at Δ2 = 3.5 meV on the outer electron-like sheets. This structure yields a strong-coupling index of 2Δ1/kBTc = 6.3, verifying strong-coupling pairing driven by interband spin fluctuations.

Keywords: Iron-based superconductors; gap profiles; photoemission spectroscopy; London penetration depth; pairing symmetry; spin fluctuations

Manuscript Timeline: Received: April 05, 2023; Revised: June 01, 2023; Accepted: June 28, 2023; Published: July 12, 2023

Citation: Sokolov, I. R., & Morozov, V. I. (2023). Superconducting Gap Profiles and Interband Spin Fluctuations in Electron-Doped Pnictide SrFe2As2 Single Crystals. International Journal of Physics, 14(7), 49–56.