Revista Mexicana de Física

Optoelectronic and thermodynamic properties of the Yttrium filled skutterudite YFe4P12

2024-05-01T09:11:15+00:00

In this work, we sought to understand the structural, electronic, optical, and thermodynamic properties of the compound YFe₄P₁₂ using the full-potential and linear augmented plane-wave method (FP-LAPW) based on density functional theory (DFT), our calculation of the lattice parameter of this compound YFe₄P₁₂ is reasonably in good agreement with the experimental results. Calculations carried out on the electronic band structure showed that the YFe₄P₁₂ compound is classified as a direct-gap Half- half-metallic in the minority spins. Moreover, optical properties, such as the optical absorption coefficient, real and imaginary parts of the dielectric function, optical conductivity, refractive index, and optical reflectivity have been studied. The effects of pressure and temperature on the lattice parameter, heat capacities, coefficients of thermal expansion, entropy, and Debye temperature were explored using the quasi-harmonic Debye model.

First-principle study origin of ferromagnetism in non-magnetic perovskite BaSnO3 doped with 2p-X (X=C, N)

2024-01-27T19:25:00+00:00

In this study, our goal is to analyze the origin of magnetization in non magnetic cubic structure perovskite BaSnO₃ doped with 2p-X (X=C, N) using the full potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT). For the exchange and correlation potential we have applied the generalized gradient approximation (GGA) and the GGA plus-modified Becke-Johnson potential (mBJ-GGA). The results show that BaSnO₃ doped with C then with N and finally with C and N exhibit half-metallic ferromagnetism behavior with the integer magnetic moment of 1, 2 and 3 μ_B per cell respectively. The origin of the ferromagnetism that occurs within these compounds is mainly caused by the p-p hybridization between 2p-impurities and its neighboring oxygen atoms. These results allowed to conclude that doped perovskite could provide a new type of materials, called half-metallic for future spintronic devices.

Complex band structure of two-dimensional thermal wave crystals

2024-06-29T20:50:31+00:00

We investigate the complex band structure of temperature oscillations in a two-dimensional thermal wave crystal. We use the Cattaneo-Vernotte heat model to describe the thermal properties. We apply the plane wave method to calculate the complex band structure of a square lattice composed of an infinite array of square bars. We find that a complete band gap exists across the whole Brillouin zone, where temperature oscillations are forbidden. This has potential applications in thermal management, thermal cloaking, and other areas.

Numerical Investigation of G–V Measurements of metal – A Nitride GaAs junction

2024-06-12T17:14:52+00:00

In this study, a Schottky diode consisting of Au/GaN/GaAs was fabricated using a radiofrequency nitrogen plasma source. The voltage-conductance characteristics (G/ω-V) of this diode structure were investigated at room temperature.

To interpret the changes in the electrical properties of the nitrided GaAs-based Schottky structure, we developed a simulation program. This program employs a numerical model to calculate the G-V characteristics, allowing us to validate the experimental measurements conducted on the Schottky diodes.

The geometric model used in our simulation considers not only the GaN layer formed between the metal and GaAs substrate but also the density and distribution of trapped states within the band gap. The program utilizes the numerical resolution of the Poisson and continuity equations to calculate the electrostatic potential and the concentrations of both n and p mobile carriers. These parameters are then used to determine the electric charge, current, capacitance, and conductance. The simulation results were subsequently compared to the experimental measurements to ensure their accuracy.

Transport of particles in a model of 2D Rayleigh-Benard convection that conserves energy and vorticity

2024-08-20T19:55:29+00:00

In contrast with the Lorenz model for 2-dimensional Rayleigh - Bénard system, the model proposed by Howard - Krishnamurti (HK) allows the possibility of a large scale horizontally shear flow making feasible the study of particles transport. However, this model lacks conservation of energy and vorticity in the absence of forcing and dissipation. A model that incorporates conservation of energy and vorticity was proposed by A. Gluhovsky et al (GTA). We perform the linear stability analysis of this later model and study the transport process on this velocity field background and make a comparison with the features of the former model. We found that the basic bifurcation structure is retained by the GTA model and discuss the differences that they indeed have. In regard to the transport processes, the basic features found using the HK velocity field background are also kept by the GTA model. We determine the size of the rather small gap in the Rayleigh number where the transport process shift from being shear flow dominated to a Brownian diffusion process.

A4×Z2×Z4 flavor symmetry model for neutrino oscillation phenomenology

2024-04-24T08:57:41+00:00

We propose a SM extension which aims to explain the most recent experimental data on neutrino oscillation. Beside $A_4$, two Abelian symmetries $Z_2$ and $Z_4$ are supplemented to prevent some Yukawa terms to get the desired mass matrices and then give predictions for the neutrino oscillation parameters in agreement with the most recent experimental data on neutrino oscillation in 3$\sigma$ range. The model provide a predictive relation between the solar and reactor neutrino mixing angles and gives possible prediction on the Dirac CP phase and two Majorana phases as well as the eﬀective neutrino mass being in agreement with the most recent constraints.

Wheeler-DeWitt canonical quantum gravity in hydrogenoid atoms according to de Broglie-Bohm and the geodesic hypothesis. Einstein’s Quantum Field Equation

2024-04-23T18:53:45+00:00

We explore the geodesic hypothesis of orbital trajectories of the electrons in hydrogenoid atoms, in the frame of de Broglie-Bohm quantum theory. It is intended that the space-time can be curved, at very short distances, by the effect of the joint action of the energy content of the atomic system and the contribution of the electric and quantum potentials. The geodesic hypothesis would explain the non-lose of energy in the electron orbital trajectories. So we explore a conception where particles and waves interact in a closed system: the waves guide the particles and the particles generate the spacetime perturbation that acts as a wave, beyond the pilot-wave theory.

We establish the equivalence, in a local neighborhood, between the electron trajectory of an hydrogenoid atom in the Minkowskian space where the de Broglie-Bohm can be cast with its movement in a Lorentzian manifold, according to the concept of metric tangent. Through the geodesic condition and the invariance of the elemental length, we establish a relationship between some components of the metrics. But as the particles in microphysics do not follow the Einstein’s field equation, we consider the 3+1 decomposition according to ADM and the quantization in the Wheeler De Witt theory and with a so-called quantum Einstein field equation, with a decomposition of spacetime into three-dimensional sheets of a spatial character. Then we derive from the moment-energy tensor a further equation between the components of the metrics. It opens the avenue to characterize the metric by an exact solution of the Einstein’s field equations.

Generating tailored high frequency features in core collapse supernova gravitational wave signals applicable in LIGO interferometric studies

2024-06-11T14:58:39+00:00

In this article, we introduce a methodology based on an analytical model of a damped harmonic oscillator subject to random forcing to generate transient gravitational wave signals. Such a model incorporates a simulated linear high-frequency component that mirrors the growing characteristic frequency over time observed in numerical simulations of core-collapse supernova gravitational wave signals. Unlike traditional numerical simulations, the method proposed in this study requires minimal computational resources, which makes it particularly advantageous for tasks such as data analysis, detection, and reconstruction of gravitational wave transients. To verify the physical accuracy of the generated signals, they are compared against the amplitude spectral of current LIGO interferometers and a 3D numerical simulation of a core-collapse supernova gravitational wave signal from the Andresen et al. 2017 model s15.nr. The results indicate that this approach is effective in generating scalable signals that align with LIGO interferometric data, offering potential utility in various gravitational wave transient investigations.

A constant self-consistent scattering lifetime in superconducting strontium ruthenate

2024-06-10T14:17:00+00:00

In this numerical work, we find a self-consistent constant scattering superconducting lifetime for two different values of the disorder parameters, the inverse atomic strength, and the stoichiometric impurity in the triplet paired unconventional super-conductor strontium ruthenate. This finding is relevant for experimentalists given that the expressions for the ultrasound attenuation and the electronic thermal conductivity depend on the superconducting scattering lifetime, and a constant lifetime fits well nonequilibrium experimental data. Henceforth, this work helps experimentalists in their interpretation of the acquired data. Additionally, we encountered tiny imaginary parts of the self-energy that resembles the Miyake-Narikiyo tiny gap out-side the unitary elastic scattering limit, and below the threshold zero gap value of 1.0 meV.

Ab initio investigation of structural, elastic, dynamic, and electronic properties of YN binary rare earth nitride in ZB cubic phase

2024-06-24T14:56:30+00:00

This research employs ab initio calculations, utilizing the FP-LAPW method as implemented in WIEN2k and the PP-PW method in QUANTUM ESPRESSO, within the framework of the GGA-PBE approximation, to investigate the physical properties of the rare earth nitride binary YN. Structural parameters of YN are determined, yielding predictive results consistent with recent calculations. Furthermore, a comprehensive investigation into mechanical behavior and elastic properties confirms the mechanical stability of YN in its cubic ZB structure. An analysis of the anisotropy coefficient reveals its elastic anisotropy. The dynamic stability of YN is investigated through PW-scf calculations using DFPT theory, enabling the calculation of phonon spectra, frequencies, and polarization vectors. These findings affirm the stability of YN material in the B3 structure, which can be experimentally synthesized. Electronic properties are probed, showing semiconductor behavior, utilizing GGA mBJ, and YS PBE0 methods to ascertain band gap values in the B3 structure. This suggests its potential for adoption in optoelectronic and photonic devices.

Diseño de amplificadores CMOS usando gm/ID y su uso como un sistema de primer orden

2024-03-09T18:50:05+00:00

This paper presents the analysis and design of CMOS differential amplifiers using the first-order approach and sizing the transistors with the g_m/I_D methodology. The design of four amplifiers using parameters of a 130nm CMOS technology is shown, and through spice simulation basic concepts of performance and compliance specifications are verified. The comparison of the performance of the designed amplifiers, in the synthesis of an active low-pass filter, is made to show that the fundamental performance parameters of each amplifier, affects the expected performance of the circuit under design, showing that the CMOS amplifier is not general purpose but that the application takes advantage of the characteristics of the amplifier or, alternatively, the amplifier is designed to meet the requirements of the application. Finally, while each architecture is sized using the same general performance specifications, it is also true that each has a specific and unique overall performance. These differences can be obtained and understood with spice simulation, since the resources of the simulation tool are used properly. All results obtained are at room temperature.

En este trabajo se presenta el análisis y diseño de amplificadores diferenciales CMOS usando la aproximación de primer orden y dimensionando los transistores con la metodología g_m/I_D. Se muestra el diseño de cuatro amplificadores usando parámetros de una tecnología CMOS 130 nm, y mediante simulación spice se verifican conceptos básicos de desempeño y el cumplimiento de especificaciones. La comparación del desempeño de los amplificadores diseñados, en la síntesis de un filtro activo pasa-bajas, se hace para mostrar que los parámetros fundamentales de desempeño de cada amplificador, afecta el desempeño esperado del circuito bajo diseño, mostrando que el amplificador CMOS no es de propósito general sino que la aplicación aprovecha las características del amplificador o, alternativamente, el amplificador se diseña para satisfacer los requerimientos de la aplicación. Finalmente, si bien cada arquitectura se dimensiona usando las mismas especificaciones generales de desempeño, también es verdad que cada una presenta un desempeño global específico y único. Estas diferencias pueden obtenerse y entenderse con simulación spice, toda vez que se usan adecuadamente los recursos de la herramienta de simulación. Todos los resultados obtenidos son a temperatura ambiente.

Determination of the natural frequencies of ultralight carbon fiber trusses for silicon tracking systems

2024-05-23T15:31:28+00:00

In this work a method is developed to determine the natural frequency of highly-irradiated ultralight carbon fiber trusses. This method is based both in experimental acoustic measurements and the ANSYS-based modeling of the trusses. The structures under study are sensor supporting trusses widely used in silicon inner trackers of large experimental setups at LHC, FAIR and NICA.

Numerical study of P3HT-based hybrid solid-state qantum dot solar cells with CdS quantum dots employing different metal oxides using SCAPS-1D

2024-04-18T23:47:31+00:00

This study presents a comprehensive numerical investigation into solid-state quantum dot solar cells (SSQDSCs) utilizing P3HT poly(3-hexylthiophene) as both a hole transport and absorber layer employing SCAPS-1D simulation software, the research explores the performance of cells composed of FTO (Fluorine-doped Tin Oxide) as the front contact, integrated with different metal oxides (Titanium dioxide (TiO2), zinc oxide (ZnO), and tin dioxide (SnO2), CdS (Cadmium sulfide )quantum dots, P3HT, and Pt (platinum )as the back contact namely Hybrid solar cell. The thickness of each layer is systematically optimized, and the influence of various CdS quantum dots sizes is thoroughly examined. The study also dived into the characterization of interface defects at the P3HT/CdS junction, involving modifications to the electron affinity of P3HT. Additionally, the impact of metal work function variations was also investigated analyzing at each case critical parameters such as open-circuit voltage (VOC), short-circuit current density (JSC), fill factor (FF), power conversion efficiency (PCE) and quantum efficiency. The results demonstrate that optimization of these parameters has the potential to elevate solar cell efficiency to 18%. These simulation findings offer valuable insights for comparative analysis and a deeper understanding of the challenges encountered in experimental research.

First principles calculations of physical properties of the CeCu2Si2 material

2024-05-08T19:18:57+00:00

Using local density approximation functional computations, LSDA (local spin density approximation) and mBJ (modified Becke-Johnson) for exchange-correlation interactions, we examined the combination CeCu₂Si₂, concentrating on its many physical properties. This work used the WC-GGA method to compute the elastic characteristics of CeCu₂Si₂ material, and the results indicate that unstrained CeCu₂Si₂ is more brittle. The density of states exhibits the metallic character of the chemical, in agreement with the inference made from the band structure. We also assessed several optical characteristics, such as real and imaginary optical conductivity, electronic energy loss, absorption coefficient, refractive index, and extinction coefficient. We also looked at the electronic components of thermal conductivity, electrical conductivity, Seebeck coefficient, and electronic conductivity. The compound's Seebeck coefficient values are negative, indicating p-type behavior. A thorough analysis of the data is presented, along with important details regarding the CeCu₂Si₂ compound's characteristics.

Comparative analysis of performance, efficiency, and resource usage between COMSOL Multiphysics and the MPh library of Python in the simulation of physical phenomena

2024-01-31T17:19:56+00:00

MPh is a library of Python that makes possible to link the Python computer language with COMSOL Multiphysics. The use of the MPh library opens the possibility to save the computer resources employed when simulating physical phenomena and solving mathematical models and equations. In the Python command interpreter is possible to change or adjust some settings and parameters from the models created in COMSOL, and to execute the COMSOL kernel to solve those models. In this study, we compare the performance of COMSOL Multiphysics and the MPh library of Python when computing the magnetic field generated by a distribution of currents and ferromagnetic material. The metrics employed to do the comparison and the methodology to measure them are described, as well as the computer equipment where the programs ran. The results show that the execution time of the computations are similar in both software, but in the rest of the metrics, the execution in Python surpassed the execution in COMSOL. We showed that the MPh library of Python demands less CPU and RAM usage when solving the mathematical models and the files containing the solutions use less storage memory. As a conclusion, we propose the use of the MPh library of Python to improve the performance of the computer in charge of carrying out the calculations.

Theoretical model for analysis of elastic constants in orthotropic materials considering shear stress

2024-07-26T16:43:16+00:00

Nowadays, a general theoretical model to describe the mechanical behavior of anisotropic or orthotropic materials is still an open challenge. In this study, we propose a new theoretical model to determine the elastic constants of these materials considering the shear components of the stress tensor.
To analyze the consistency of new approach in biaxial stress state on thin films, we used data reported in the literature, based in the $\sin^2 \psi$ technique. For the first time, the shear modulus value equal to $G_{xz} = 0.3 GPa$, for a polycrystalline Au thin film, was calculated, in addition to other elastic constants. Finally, we demonstrate that the new proposal theoretical model considering shear stress can be useful to determine elastic constants in orthotropic materials from experimentally measured data.

A non-newtonian approach to geometric phase through optic fiber via multiplicative quaternions

2024-06-15T23:49:20+00:00

In this paper, we researched magnetic and electromagnetic curves in multiplicative Euclidean 3-space via multiplicative quaternion algebra. Firstly, we examined the geometric phase representation of the polarized light wave in the optic fiber by multiplicative Frenet frame. Using the quaternionic approaches, we were able to derive the magnetic curve equations and theorems. Then, three particular instances have been illustrated with examples of electromagnetic curves and magnetic field equations. Lastly, we provided an interpretation of the findings. With the help of the results, we were able to present an alternative viewpoint on the construction of trajectories (such as circular or spiral-like ones) that do not exist uniquely in the realm of physics.

Drug expiration study using Raman spectroscopy and super paramagnetic clustering

2024-07-11T18:29:26+00:00

Currently, there is a belief that drugs used after the expiration date no longer work, or even these can cause some damage. In the present work, several types of drugs on the market with different expiration dates are analyzed to find out if these, with the expired expiration date, present spectroscopic differences from those drugs whose expiration date is still valid. This study used the Raman spectroscopy technique to determine the chemical composition of drugs. To measure the drug Raman spectra, Horiba equipment, LabRam HR800, was used with an Olympus confocal microscope focusing a laser of 830 nm and 17 mW on the drugs through a 50 X Leica long-range objective. The Super Paramagnetic Clustering (SPC) method was applied to classify the Raman spectra. In the SPC method, the clustering process is based on a phenomenon of clustering observed in nature at the atomic level and perfectly described by a statistical physics model known as the Potts model, which describes the interacting spins on a crystalline lattice. This clustering method allows for identifying hierarchical structures in the spectra data banks. Fourteen drugs were analyzed, including 2 capsules, 5 tablets, 2 liquid samples, 4 ointments, and one spray with 1 to 3 expired expiration dates. Comparing drugs with expiration dates that are still valid and expired, the SPC results applied to the Raman spectra showed that, although some drugs indicated chemical differences, others indicated no chemical differences, even among those with up to two expired expiration dates. The results showed that Raman spectroscopy and SPC are excellent tools for discriminating between expired and non-expired drugs. The Principal Components Analysis (PCA) was also applied as a cross-checking method of the SPC result, obtaining consistent results. To our knowledge, it is the first preliminary result evaluating the usefulness of Raman spectroscopy and SPC in identifying expired drugs distributed on the market.