International Journal of Physics | Vol. 7, No. 6, June 2016 | pp. 41–48
DOI: 10.46882/2016/IJP/000074
Research Article
Title: High-Pressure Elastic Moduli and Structural Stability of Ultra-Incompressible Tungsten Tetraboride
Names of Authors: V. I. Morozov¹, K. A. Tanaka²
Authors’ Affiliations: ¹Institute of High Pressure Physics, Russian Academy of Sciences, Troitsk, Russia; ²Department 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 orthorhombic tungsten tetraboride (WB4) 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 = 328.0 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, C22, C33, C44, C55, and C66) 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 and b-axis, which is due to short, covalent tungsten-boron bonds aligned along the plane. The electronic structure calculations show a high density of states at the Fermi level, indicating that WB4 retains its metallic character under high pressure. These precise elastic profiles confirm the potential of transition metal borides as viable alternatives to diamond-based superhard materials.
Keywords: Tungsten tetraboride; density functional theory; elastic constants; high pressure; mechanical stability; directional compressibility
Manuscript Timeline: Received: February 15, 2016; Revised: April 12, 2016; Accepted: May 04, 2016; Published: June 15, 2016
Citation: Morozov, V. I., & Tanaka, K. A. (2016). High-Pressure Elastic Moduli and Structural Stability of Ultra-Incompressible Tungsten Tetraboride. International Journal of Physics, 7(6), 41–48.
International Journal of Physics | Vol. 7, No. 5, May 2016 | pp. 33–40
DOI: 10.46882/2016/IJP/000073
Research Article
Title: Resonant Energy Transfer Dynamics between Colloidal InP/ZnS Quantum Dots and Monolayer Molybdenum Diselenide
Names of Authors: T. H. Nguyen¹, P. L. Becker²
Authors’ Affiliations: ¹Department of Physics, Vietnam National University, Hanoi, Vietnam; ²Institute 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 indium phosphide zinc sulfide (InP/ZnS) core-shell quantum dots and monolayer molybdenum diselenide (MoSe²). 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 MoSe² monolayer. Concurrently, the average fluorescence lifetime of the InP/ZnS 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 MoSe² 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: January 20, 2016; Revised: March 05, 2016; Accepted: April 02, 2016; Published: May 12, 2016
Citation: Nguyen, T. H., & Becker, P. L. (2016). Resonant Energy Transfer Dynamics between Colloidal InP/ZnS Quantum Dots and Monolayer Molybdenum Diselenide. International Journal of Physics, 7(5), 33–40.
International Journal of Physics | Vol. 7, No. 4, April 2016 | pp. 25–32
DOI: 10.46882/2016/IJP/000072
Research Article
Title: Density Functional Theory Analysis of Catalytic Nitrogen Reduction on Metal-Free Boron-Doped Graphene Layers
Names of Authors: A. L. Silva¹, Y. W. Zhang²
Authors’ Affiliations: ¹Institute of Physics, Federal University of Rio Grande do Sul, Porto Alegre, Brazil; ²Department 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 boron-doped graphene surfaces. We modeled three distinct configurations: single boron substitution, double boron substitution, and boron-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 boron-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 boron vacancy sites was estimated at -0.42 V versus the standard hydrogen electrode. Charge density difference mappings show that boron 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; boron-doped graphene; electrocatalysis; reaction mechanism; overpotential
Manuscript Timeline: Received: January 04, 2016; Revised: February 17, 2016; Accepted: March 09, 2016; Published: April 07, 2016
Citation: Silva, A. L., & Zhang, Y. W. (2016). Density Functional Theory Analysis of Catalytic Nitrogen Reduction on Metal-Free Boron-Doped Graphene Layers. International Journal of Physics, 7(4), 25–32.
International Journal of Physics | Vol. 7, No. 3, March 2016 | pp. 17–24
DOI: 10.46882/2016/IJP/000071
Research Article
Title: Finite Element Modeling of Acoustic Wave Attenuation in Saturated Porous Concrete with Viscoelastic Liners
Names of Authors: P. J. O’Connor¹, L. A. O’Connor²
Authors’ Affiliations: ¹Department of Civil and Environmental Engineering, University College Cork, Cork, Ireland; ²School of Cosmic Physics, Dublin Institute for Advanced Studies, Dublin, Ireland
Abstract: Characterizing 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 liners. 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: November 27, 2015; Revised: January 15, 2016; Accepted: February 05, 2016; Published: March 11, 2016
Citation: O’Connor, P. J., & O’Connor, L. A. (2016). Finite Element Modeling of Acoustic Wave Attenuation in Saturated Porous Concrete with Viscoelastic Liners. International Journal of Physics, 7(3), 17–24.
International Journal of Physics | Vol. 7, No. 2, February 2016 | pp. 9–16
DOI: 10.46882/2016/IJP/000070
Research Article
Title: Fluid Velocity Mapping and Magnetic Reconnection Dynamics in Solar Flares via Space-Based Extreme Ultraviolet Spectroscopy
Names of Authors: G. R. Davies¹, F. E. Silva²
Authors’ Affiliations: ¹School of Physics and Astronomy, University of St Andrews, St Andrews, UK; ²Department of Applied Physics, University of São Paulo, São Paulo, Brazil
Abstract: Magnetic reconnection is the primary physical process driving explosive energy releases in solar atmospheric plasma, heating material to millions of Kelvin and accelerating coronal mass ejections. This paper evaluates fluid velocity mapping and quantifies local magnetic reconnection rates within an M-class solar flare event. We utilized high-resolution spectroscopic data from space-based extreme ultraviolet (EUV) channels tracking highly ionized iron lines (Fe XVI and Fe XXIV). Differential affine velocity estimator algorithms were deployed to construct two-dimensional velocity fields of plasma inflows and outflows surrounding the current sheet. The empirical measurements reveal systematic plasma inflows moving at 18.2 km/s, while directed outflows reach velocities of 285.0 km/s along the coronal loop headers. Based on these transport metrics, the local dimensionless reconnection rate was calculated to range between 0.05 and 0.08. 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 9.2 MK within the diffusion region, confirming intense localized viscous dissipation. These imaging diagnostics provide direct observational parameters for refining magnetohydrodynamic models of solar coronal heating loops.
Keywords: Solar corona; magnetic reconnection; extreme ultraviolet; plasma dynamics; solar flares; magnetohydrodynamics
Manuscript Timeline: Received: November 02, 2015; Revised: December 18, 2015; Accepted: January 11, 2016; Published: February 08, 2016
Citation: Davies, G. R., & Silva, F. E. (2016). Fluid Velocity Mapping and Magnetic Reconnection Dynamics in Solar Flares via Space-Based Extreme Ultraviolet Spectroscopy. International Journal of Physics, 7(2), 9–16.
International Journal of Physics | Vol. 7, No. 1, January 2016 | pp. 1–8
DOI: 10.46882/2016/IJP/000069
Research Article
Title: Optical Properties and Exciton-Polariton Dynamics of Monolayer Tungsten Disulfide on Plasmonic Nanogate Arrays
Names of Authors: Y. S. Kim¹, M. G. Nielsen²
Authors’ Affiliations: ¹Department of Physics and Astronomy, Seoul National University, Seoul, South Korea; ²Department of Physics and Astronomy, Aarhus University, Aarhus, Denmark
Abstract: Monolayer transition metal dichalcogenides have attracted significant interest due to their strong light-matter interactions and potential for nanoscale valleytronic devices. This study characterizes the optical properties and exciton-polariton dynamics of monolayer tungsten disulfide (WS²) integrated onto plasmonic gold nanogate arrays. The monolayer flakes were synthesized via chemical vapor deposition and transferred onto the nanostructured substrates using a dry-transfer technique. We performed micro-photoluminescence and angle-resolved reflectivity measurements under mechanical tensile strains from 0.0% to 1.8% at a room temperature of 300 K. The unstrained monolayer coupled to the plasmonic array exhibits a strong Rabi splitting of 45.0 meV, confirming the transition into the strong light-matter coupling regime. Applying a 1.2% tensile strain shifts the exciton resonance energy from 2.01 eV to 1.94 eV, yielding a strain tuning factor of 58.3 meV/% strain. Time-resolved photoluminescence spectroscopy revealed a shortened polariton decay lifetime, dropping from 14.5 ps down to 4.2 ps due to the plasmonic Purcell effect. Our numerical models confirm that the localized electromagnetic field enhancement within the nanogates increases the exciton-photon coupling rate by 40.0%. These findings demonstrate that plasmonic strain engineering offers an effective route for controlling exciton-polariton states in thin-film optoelectronic architectures.
Keywords: Tungsten disulfide; plasmonic nanogates; photoluminescence; exciton-polariton; tensile strain; light-matter coupling
Manuscript Timeline: Received: October 12, 2015; Revised: November 24, 2015; Accepted: December 15, 2015; Published: January 12, 2016
Citation: Kim, Y. S., & Nielsen, M. G. (2016). Optical Properties and Exciton-Polariton Dynamics of Monolayer Tungsten Disulfide on Plasmonic Nanogate Arrays. International Journal of Physics, 7(1), 1–8.