International Journal of Physics

International Journal of Physics | Vol. 11, No. 6, June 2020 | pp. 41–48

DOI: 10.46882/2020/IJP/000122

Research Article

Title: Relativistic Hydrodynamic Modeling of Particle Production Cascades in Asymmetric Oxygen-Lead Collisions

Names of Authors: H. L. Mueller¹, A. M. El-Sayed²

Authors’ Affiliations:
¹ Institut für Kernphysik, Karlsruher Institut für Technologie, Karlsruhe, Germany
² Department of Physics, Faculty of Science, Ain Shams University, Cairo, Egypt

Abstract: Asymmetric oxygen-lead (O-Pb) collisions provide a crucial baseline for isolating cold nuclear matter effects from the collective signature of the quark-gluon plasma in intermediate systems. This study presents a relativistic hydrodynamic modeling framework to simulate particle production cascades in O-Pb collisions at a center-of-mass energy of 5.02 TeV per nucleon pair. We utilized a 3+1 dimensional viscous hydrodynamic code coupled with a statistical hadronization module to compute transverse momentum spectra and azimuthal anisotropy coefficients. The initial energy density profiles were generated using a Glauber-Gribov color-fluctuation model to capture sub-nucleon scale configurations. The numerical simulations show that expanding systems build a substantial radial flow profile, which shifts the mean transverse momentum of protons up to 1.38 GeV/c in high-multiplicity events. The calculated elliptic flow coefficient (v²) displays a strong mass-ordering effect, which matches experimental measurements gathered by LHC tracking arrays within a tight ±6.0% margin. This close agreement suggests that small-scale heavy-ion systems generated in O-Pb collisions can achieve brief hydrodynamic collective expansion. These findings help clarify the boundaries of fluid-like behavior in high-energy subatomic particle interactions.

Keywords: Relativistic hydrodynamics; particle production; oxygen-lead collisions; elliptic flow; color-fluctuation model; statistical hadronization

Manuscript Timeline: Received: February 15, 2020; Revised: April 12, 2020; Accepted: May 04, 2020; Published: June 15, 2020

Citation: Mueller, H. L., & El-Sayed, A. M. (2020). Relativistic Hydrodynamic Modeling of Particle Production Cascades in Asymmetric Oxygen-Lead Collisions. International Journal of Physics, 11(6), 41–48.

International Journal of Physics | Vol. 11, No. 5, May 2020 | pp. 33–40

DOI: 10.46882/2020/IJP/000121

Research Article

Title: Kinetic Simulation of Electron Transport Parameters and Dissociation Profiles in Low-Pressure Carbon Dioxide-Nitrogen Plasmas

Names of Authors: A. M. El-Chemali¹, J. L. Manceau²

Authors’ Affiliations:
¹ Department of Physics, Faculty of Science, Lebanese University, Beirut, Lebanon
² Laboratoire Kastler Brossel, Sorbonne Université, CNRS, Paris, France

Abstract: Carbon dioxide-nitrogen (CO²-N²) gas mixtures are widely utilized in plasma processing reactors, environmental mitigation chambers, and gas discharge lasers. This study develops a self-consistent kinetic simulation model to analyze electron transport properties and compute dissociation profiles in low-pressure CO²-N² gas mixtures. We solved the electron Boltzmann equation using a multi-term spherical harmonic expansion scheme across a reduced electric field range (E/N) from 2.0 Td to 500.0 Td. The model incorporates comprehensive cross-section sets, including elastic scattering, electronic excitation, and direct impact ionization, while accounting for vibrational exchange processes. Our modeling results show that adding nitrogen fractions (from 10.0% to 50.0% by volume) drastically distorts the electron energy distribution function. At a field strength of E/N = 40.0 Td, the total dissociation rate coefficient increases significantly in the 50% CO² - 50% N² mixture compared to pure carbon dioxide. This enhancement is driven by resonant energy transfer between metastable nitrogen vibrational states and the ground-state carbon dioxide molecules. The calculated electron drift velocities match independent swarm experimental measurements within a ±4.5% variance. These kinetic parameters provide essential baseline input data for optimizing industrial plasma conversion systems.

Keywords: Carbon dioxide mixtures; Boltzmann equation; electron transport; plasma kinetics; cross-section; plasma modeling

Manuscript Timeline: Received: January 20, 2020; Revised: March 05, 2020; Accepted: April 02, 2020; Published: May 12, 2020

Citation: El-Chemali, A. M., & Manceau, J. L. (2020). Kinetic Simulation of Electron Transport Parameters and Dissociation Profiles in Low-Pressure Carbon Dioxide-Nitrogen Plasmas. International Journal of Physics, 11(5), 33–40.

International Journal of Physics | Vol. 11, No. 4, April 2020 | pp. 25–32

DOI: 10.46882/2020/IJP/000120

Research Article

Title: High-Pressure Elastic Moduli and Structural Stability of Ultra-Incompressible Molybdenum Disilicide

Names of Authors: V. I. Morozov¹, K. A. Tanaka²

Authors’ Affiliations:
¹ Institute of High Pressure Physics, Russian Academy of Sciences, Troitsk, Russia
² Department of Physics, Tokyo Institute of Technology, Tokyo, Japan

Abstract: Designing ultra-incompressible structural materials capable of withstanding extreme mechanical stress is vital for industrial tooling and high-pressure research components. This paper examines the high-pressure elastic moduli and structural stability of tetragonal molybdenum disilicide (MoSi²) up to hydrostatic pressures of 130.0 GPa. We performed first-principles density functional theory computations within the generalized gradient approximation framework. At zero pressure, the calculated bulk modulus is B0 = 215.0 GPa, with an elastic derivative value of B0' = 4.15. These results match experimental diamond anvil cell measurements within a 1.5% margin. The single-crystal elastic constants (C11, C33, C44, C66, C12, and C13) increase monotonically under compression, satisfying all Born mechanical stability conditions across the tested pressure range. The directional compressibility curves reveal that the crystal c-axis is significantly stiffer than the a-axis, which is due to short, covalent molybdenum-silicon bonds aligned along the plane. The electronic structure calculations show a high density of states at the Fermi level, indicating that MoSi² retains its metallic character under high pressure. These precise elastic profiles confirm the potential of transition metal silicides as viable alternatives to conventional superhard materials.

Keywords: Molybdenum disilicide; density functional theory; elastic constants; high pressure; mechanical stability; directional compressibility

Manuscript Timeline: Received: January 04, 2020; Revised: February 17, 2020; Accepted: March 09, 2020; Published: April 10, 2020

Citation: Morozov, V. I., & Tanaka, K. A. (2020). High-Pressure Elastic Moduli and Structural Stability of Ultra-Incompressible Molybdenum Disilicide. International Journal of Physics, 11(4), 25–32.

International Journal of Physics | Vol. 11, No. 3, March 2020 | pp. 17–24

DOI: 10.46882/2020/IJP/000119

Research Article

Title: Resonant Energy Transfer Dynamics between Colloidal Perovskite Quantum Dots and Monolayer Tungsten Diselenide

Names of Authors: T. H. Nguyen¹, P. L. Becker²

Authors’ Affiliations:
¹ Department of Physics, Vietnam National University, Hanoi, Vietnam
² Institute for Plasma Research, University of Stuttgart, Stuttgart, Germany

Abstract: Hybrid semiconductor nanostructures combining zero-dimensional quantum dots and two-dimensional materials provide new opportunities for developing advanced light-harvesting systems. This paper examines the non-radiative Förster resonant energy transfer (FRET) dynamics between colloidal perovskite (CsPbBr3) quantum dots and monolayer tungsten diselenide (WSe²). The hybrid interfaces were fabricated via sequential spin-coating routines onto quartz substrates. We performed steady-state photoluminescence and time-resolved single-photon counting measurements at an operating temperature of 300 K. The experimental data reveal a strong 82.0% quenching of the quantum dot photoluminescence emission when coupled to the WSe² monolayer. Concurrently, the average fluorescence lifetime of the quantum dots decreased from 6.2 ns down to 1.12 ns. This lifetime reduction yields a calculated FRET efficiency of 81.9% with a corresponding energy transfer rate of 0.73 ns⁻¹. The donor-acceptor separation distance was estimated to be 3.8 nm using the standard Förster mathematical model. Spectral overlap analysis confirms that energy transfer is mediated by the alignment between quantum dot emission and the WSe² exciton absorption bands. These rapid energy transfer dynamics show that quantum dot sensitization can significantly enhance light absorption in ultra-thin optoelectronic architectures.

Keywords: Quantum dots; transition metal dichalcogenides; resonant energy transfer; fluorescence lifetime; hybrid nanostructures; optoelectronics

Manuscript Timeline: Received: December 14, 2019; Revised: January 20, 2020; Accepted: February 08, 2020; Published: March 11, 2020

Citation: Nguyen, T. H., & Becker, P. L. (2020). Resonant Energy Transfer Dynamics between Colloidal Perovskite Quantum Dots and Monolayer Tungsten Diselenide. International Journal of Physics, 11(3), 17–24.

International Journal of Physics | Vol. 11, No. 2, February 2020 | pp. 9–16

DOI: 10.46882/2020/IJP/000118

Research Article

Title: Density Functional Theory Analysis of Catalytic Nitrogen Reduction on Metal-Free Nitrogen-Doped Graphene Inclusions

Names of Authors: A. L. Silva¹, Y. W. Zhang²

Authors’ Affiliations:
¹ Institute of Physics, Federal University of Rio Grande do Sul, Porto Alegre, Brazil
² Department of Physics, Tsinghua University, Beijing, China

Abstract: Electrochemical reduction of nitrogen (N²) into ammonia under ambient conditions offers a green alternative to the energy-intensive industrial Haber-Bosch process. This investigation uses density functional theory calculations to analyze the catalytic performance and reaction mechanisms of nitrogen reduction on metal-free nitrogen-doped graphene inclusions. We modeled three distinct configurations: single nitrogen substitution, double nitrogen substitution, and nitrogen-doped vacancy sites. Free energy profiles for intermediate steps leading to ammonia (NH3) were computed using the computational hydrogen electrode model across both enzymatic and consecutive pathways. The calculations demonstrate that nitrogen-doped vacancy sites lower the activation barrier for the rate-limiting nitrogenation step (*N² + H⁺ + e⁻ -> *NNH) to 0.52 eV. This value is significantly lower than the 1.45 eV barrier calculated for pristine graphene sheets. The overpotential required to trigger selective ammonia production on nitrogen vacancy sites was estimated at -0.42 V versus the standard hydrogen electrode. Charge density difference mappings show that nitrogen doping induces localized 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 ambient ammonia synthesis.

Keywords: Nitrogen reduction; density functional theory; nitrogen-doped graphene; electrocatalysis; reaction mechanism; overpotential

Manuscript Timeline: Received: November 02, 2019; Revised: December 18, 2019; Accepted: January 11, 2020; Published: February 14, 2020

Citation: Silva, A. L., & Zhang, Y. W. (2020). Density Functional Theory Analysis of Catalytic Nitrogen Reduction on Metal-Free Nitrogen-Doped Graphene Inclusions. International Journal of Physics, 11(2), 9–16.

International Journal of Physics | Vol. 11, No. 1, January 2020 | pp. 1–8

DOI: 10.46882/2020/IJP/000117

Research Article

Title: Finite Element Modeling of Acoustic Wave Scattering in Saturated Porous Media with Viscoelastic Layered Metamaterials

Names of Authors: P. J. O’Connor¹, H. J. Mueller²

Authors’ Affiliations:
¹ Department of Civil and Environmental Engineering, University College Cork, Cork, Ireland
² Institute of Physics, Karlsruher Institut für Technologie, Karlsruhe, Germany

Abstract: Characterising elastic wave propagation through fluid-saturated porous structures is crucial for industrial noise mitigation and optimizing deep-earth structural foundations. This study presents a finite element modeling approach to simulate acoustic wave attenuation within a saturated porous concrete matrix containing embedded viscoelastic layered metamaterials. The mathematical model integrates Biot's dynamic equations of poroelasticity with a generalized Maxwell constitutive framework to account for viscoelastic relaxation. Numerical simulations were executed across an ultrasonic frequency spectrum from 10.0 kHz to 500.0 kHz. The computational results demonstrate that the presence of viscoelastic liners induces a strong attenuation peak for the fast compressional wave mode at 165.0 kHz. This attenuation is primarily driven by local fluid flow mechanisms at the matrix-liner interfaces. The scattering cross-section displays a non-linear dependence on liner thickness fractions, showing saturation behavior above a 12.0% threshold. Experimental validation was conducted using synthetic porous concrete specimens filled with silicone rubber membranes. The measured transmission loss spectra matched the simulated profiles within a ±5.5% margin. These findings help optimize acoustic barriers and improve interpretations of seismic data collected from fluid-bearing geological formations.

Keywords: Porous media; acoustic scattering; finite element modeling; Biot's theory; viscoelasticity; wave attenuation

Manuscript Timeline: Received: October 12, 2019; Revised: November 24, 2019; Accepted: December 15, 2019; Published: January 15, 2020

Citation: O’Connor, P. J., & Mueller, H. J. (2020). Finite Element Modeling of Acoustic Wave Scattering in Saturated Porous Media with Viscoelastic Layered Metamaterials. International Journal of Physics, 11(1), 1–8.