Vol. 71 No. 4 Jul-Aug (2025): Revista Mexicana de Física

The all-electron full-potential linearized augmented plane-wave method is used to investigate the structural, electronic, and thermodynamic properties of the hexagonal structure of Ni₂P. We show that Ni₂P is stable and has interesting mechanical and thermodynamical properties. While we used the non-equilibrium Green’s function formalism to investigate electronic transport properties, particularly conductance by constructing a symmetric junction with Ni₂P acting as the spacer between two gold electrodes (Au/Ni₂P/Au). We considered both phosphorus-rich and phosphorus-poor terminated interface and we show that the transmission coefficients depends on the nature of Ni₂P/Au interface. Furthermore, we mimic experimental junction, by analyzing the impact of phosphorus deficiency. We show that Ni₂P’s conductance is altered differently depending on whether the defect is located at the interface or deep within the spacer.

Using the FP-LAPW method with the exchange and correlation potentials of the GGA and mBJ-GGA approximations, we have studied the structural, electronic, thermoelectric, and optical properties of the double perovskite halide compound K₂AgInCl₆. Our results indicate that this compound is stable in the nonmagnetic phase and exhibits structural stability according to the normative values ​​of the Goldsmith factor (t) and octahedral factor (μ). It is thermodynamically stable, as evidenced by negative formation energy. K₂AgInCl₆ acts as a semiconductor, displaying a direct band gap of 1.162 eV in GGA and 2.944 eV in mBJ-GGA. Thermoelectric analysis reveals excellent properties, with ZT values ​​close to unity, but nevertheless, the GGA approximation performs well at medium and high temperatures (300-800 K), while mBJ-GGA is more efficient at lower temperatures (50-100 K), with ZTs ranging from 0.73 to 0.7 for the latter approximation. In addition, K₂AgInCl₆ shows transparency in the infrared and visible spectrums, as well as strong absorption and reflectivity in the UV spectrum, making it suitable for various applications, including in broadband solar cells to improve efficiency through extended absorption. In optoelectronics, it can serve as a UV light emitter in high-power LEDs and potentially as a UV filter to protect materials and people from harmful radiation.

In this study, we present numerical simulations of the flow-induced deflection of a microcantilever beam and the distribution of a passive analyte inside a microfluidic cell for a piezoresistive biosensor. The numerical implementation was validated using semi-analytical models and previously reported experimental measurements. The primary objective of the study is to understand the impact of the flow on the cantilever's behavior and use this knowledge in the decision-making process for a microfluidic cell design for a piezoresistive biosensor. To accomplish this, the results for three different inlet/outlet configurations allow us to describe the dynamics of the fluid-structure interaction, finding that, for small times, the flow is symmetrical around the microcantilever. As time passes, two vortices surround the microcantilever, resulting in an asymmetric flow distribution. Throughout the entire range of analyzed inlet flow rates, it is evident that the inlet/outlet configuration significantly influences the deflection and stress sustained by the cantilever. Similarly, these configurations affect how the concentration of an analyte sample distributes on the detecting surface. The in-depth understanding of the flow dynamics within the microfluidic cell and its effect on the cantilever, as provided by the simulations, can be used to propose design recommendations aimed at reducing the noise due to the flow, ultimately achieving high sensitivity in these types of devices.

This paper revisits the send/retrieve message process using synchronization of the Lorenz system with a monochromatic message. We analyze how the fidelity of the retrieved signal depends on the message frequency and demonstrate message hacking through Fourier spectrum analysis. Various parameters affecting fidelity and noise in the hacked signal are also examined. Additionally, we transmit text messages recovered through synchronization and investigate their vulnerability to hacking. As a countermeasure, we propose a method to send both types of messages using the convolution as the encryption function to hide the message in the chaotic signal. This approach enhances retrieval fidelity and significantly increases resistance to hacking compared to synchronization-based methods.

We study the localization-delocalization of a particle moving within a circular region of radius r₀  from a theoretical information point of view. We computed the Shannon entropy, Fisher information  and disequilibrium in configuration and momentum spaces for a collection of stationary states.  Comparing our results of Shannon entropies with those previously published we found good agreement  with those. Shannon entropy, Fisher information and the disequilibrium offer complementary results for the description of the particle localization-delocalization.

Integrated intensity ratios of second- to first-order X-ray reflections were measured from a strongly textured pure silver sample, oriented at the maximum pole density, using several wavelengths. This was done to determine whether extinction exists in strongly textured polycrystals, as suggested by pole figure measurements, where pole density maxima of the second-order reflection often exceeds those of the first-order reflection. The integrated intensities of the reflections were normalized using the corresponding integrated intensities from a powder sample. The dominant texture of the silver sample was [110]< 011 >, and the ratios were measured for the 111 and 222 reflection pairs. All resulting ratios were larger than 1, indicating the presence of extinction, which affects first-order reflections more significantly than second-order reflections. Considering the larger number of possible reflections of a polycrystal compared to the few number of reflections of a single crystal, double diffraction between different grains is proposed here as the cause of the observed effect, similar to the well-known secondary extinction in single crystals. To investigate whether a texture gradient could influence the results, EBSD observations were conducted on the sample. A heterogeneous texture was revealed at the edges, but these heterogeneities were not found to affect the results.

This work studies possible morphologies present in fractal foams with dual pore distribution, focalizing the analysis in features characterizing the pore network. These studies were conducted using foams modelled through the combined use of Discrete and Finite Element Methods (DEM and FEM, respectively). DEM was used to generate pore coordinates, for in a second step modelling pores of varied sizes using FEM. These models allowed to obtain fractal foams with morphologies closer to real experimental foams, which is essential for the subsequent estimation of their mechanical properties through FEM. Using different measurement methods, some analyzes were carried out, such as the effect of the dimension of the Representative Volume Element (RVE) on the porosity percentage, the number of nodes until a convergent behavior, the interconnectivity of the pores, the importance of the pore wall thickness and the fractal dimension determination. The effect of these parameters on the simulated mechanical properties of the foams was analyzed throw the use of FEM.

Zinc oxide (ZnO) thin films and ZnO nanorod thin films were prepared via sol-gel and chemical bath deposition methods at low temperatures, respectively, and tested for their ability to photocatalytically degrade Methylene Blue. Both films were oriented in the c-axis in the (002) plane, but the crystallinity of the ZnO nanorod film was better than the ZnO seed layer. The surface morphology of the ZnO film was in ripple form, allowing the ZnO-nanorods to grow around the ripples and increase the contact area with the solution. The ZnO nanorod film enhances the adsorption process. After 2.49 hours of irradiation, 50% of the dye degrades, and 80% degrades after 6 hours. The structural properties, such as good crystallinity and the orientation in the (002) plane, help improve the films’ photocatalytic efficiency. ZnO and ZnO-nanorod films could be considered efficient and green options for the photocatalytic process of decomposing organic pollutants in an aqueous medium.

In this paper, we report the effect of poly (vinyl alcohol) (PVA)/poly (vinyl pyrrolidone) (PVP) blend with different concentration (10, 20, 30 and 40) wt % of  AgNO₃    preparation using the casting method . We conducted the characterization of Ag nanoparticles using Fourier transform infrared spectroscopy (FTIR) and (UV-VIS) spectroscopy. We specifically investigated the nanoparticles using UV-Vis spectroscopy in the spectral range of 200–900 nm. We established the energy gap of indirect permitted transitions and observed a decrease in their values as the concentration of nanoparticles increased. This study prepared a nanopolymer composite solution consisting of PVA-PVP-AgNO₃. We tested the sensitivity of the bacteria S. aureus, S. epidermidis, E. coli, P. aeruginosa, and C. albicans to this solution. Practical results have shown that the nanopolymer composite solution is highly effective in eliminating and restricting the growth of these bacteria.

Polyacetylene was synthesized by using Ziegler-Natta catalyst with chemical polymerization method and doped it with 10% iodine and 10% bromine to prepared the composites. The samples were characterized by XRD, SEM and temperature dependent DC electrical conductivity. The XRD pattern of doped polyacetylene displayed that the crystallinity was improved. The SEM morphology of doped polyacetylene demonstrated that granularity was increased. The calculated electrical conductivity shows the low electric conductivity of pure polyacetylene but when we doped polyacetylene with iodine and bromine the electrical conductivity was improved. This study explored that the improvement in the electrical conductivity which may confirm the doped polyacetylene behave as semiconductor and can by helpful for the potential application of devices and related fields.

In this work, we present a comprehensive investigation regarding the physical properties of Mg_xCd_1-xO ternary alloys for different concentrations (0≤x≤1), in rock salt phase. These properties, including structural, electronic, and optical properties, were studied using the full-potential linearized augmented plane wave (FP-LAPW) method based on the density functional theory (DFT) with the Wien2k code. The structural parameters of RS Mg_xCd_1-xO are studied in detail as a function of Mg concentration using the generalized gradient approximation (GGA–PBEsol). The calculated structural parameters of both binaries are in good agreement with their corresponding theoretical and experimental data. The results show that the value of the lattice parameter of RS Mg_xCd_1-xO decreases almost linearly with the increasing Mg concentration and exhibits a small deviation from the linear composition dependence (LCD). Both approximations (LDA) and (TB-mBJ) were used to explore the electronic properties. It is found that the increasing Mg concentration leads to increasing energy band gap. Our obtained results demonstrate that the RS CdO has an indirect band gaps and RS MgO has a direct band gap, while RS Mg_xCd_1-xO ternaries (0.125 ≤ x ≤ 0.875) exhibit an indirect band gap semiconductors. Additionally, the linear optical properties including, complex dielectric function, complex refractive index, absorption coefficient, optical conductivity and absorption coefficient, are calculated and discussed in detail. Our obtained results are discussed in detail and compared with existing data in the literature. These results confirm that the RS Mg_xCd_1-xO ternary alloys are a promising candidate for ultraviolet photo electronic devices.

TheMulti-Purpose Detector (MPD) is one of the three experiments of the Nuclotron Ion Collider-fAcility (NICA) complex, which is currently under construction at the Joint Institute for Nuclear Research in Dubna. With collisions of heavy ions in the collider mode, the MPD will cover the energy range √sNN = 4 − 11 GeV to scan the high baryon-density region of the QCD phase diagram. With expected statistics of 50–100 million events collected during the first run, MPD will be able to study a number of observables, including measurements of light hadrons and (hyper)nuclei production, particle flow, correlations and fluctuations, have a first look at dielectron production, and modification of vector-meson properties in dense matter. In this paper, we present selected results of the physics feasibility studies for theMPD experiment in Bi+Bi collisions at √sNN = 9.2 GeV, the system considered as one of the first available at the NICA collider.

We present a new family of Bessel solutions of the paraxial equation. Such solutions keep their form during propagation because of a quadratic phase factor that makes them scaled propagation invariant fields. When a Gaussian support is incorporated, the solution loses its invariant properties, although, over some volume, it closely resembles a scaled propagation invariant field. The Bessel beams we introduce have the particularity that they present a very strong focusing effect and do not necessarily require a Gaussian support.

In this study, we investigate the perturbed Fokas-Lenells equation with conformable fractional derivatives in the presence of white noise, employing two advanced methodologies. The analysis utilizes Hermite and inverse Hermite transformations within the framework of white noise theory to derive solutions to the model. We also construct traveling wave solutions, optical soliton solutions, and their respective stochastic counterparts.

Atomic layer deposition (ALD) is a versatile technique to grow thin films for a wide range of applications including energy conversion and electronics. Materials deposited on insulating platforms through ALD can expand their use in optics and photonics. In this work, we present the design of an integrated optics all-pass micro-ring resonators based on measured optical properties of ALD materials, particularly, titanium- and zinc oxides (TiO2 and ZnO on insulator). For optical communication applications, zinc oxide on an insulator (ZOI) provides mode confinement of 46%, an evanescent decay of 855 nm, and a quality factor of up to 104 at 1550 nm. Atomic layer deposited core materials on an insulator provide an effective alternative for optics and photonics.

Colloidal quantum dots (CQDs) with variable narrow bandgaps have emerged as powerful competitors to epitaxially grown semiconductors in the domain of infrared light transitions. This class of materials holds great promise for the development of next-generation optoelectronic devices, especially photodetectors. In recent developments, the use of silver chalcogenide CQDs has extended into biomedical applications of quantum dots. This expansion is attributed to their advantageous properties, such as low toxicity and tunable intraband transitions reaching the mid-infrared window. In this research, we investigate a structure for mid-infrared photon detection in the form of an intraband Ag₂Se-PbS colloidal quantum dot (CQD) photodetector. Detectivity, a crucial performance parameter, is enhanced through numerical optimization by manipulating key design parameters such as Ag₂Se CQD diameter, Ag₂Se film doping density, and the number of PbS CQD layers in the barrier layer of the device's active region. This optimization process is conducted at various temperatures and biases. The results reveal that, under conditions of a 1 V bias and 80 K, the designed Ag₂Se-PbS CQD infrared photodetector achieves peak detectivities. Specifically, observed peak detectivities of 13.13×10⁹ Jones for Ag₂Se CQDs with a diameter of 3.7 nm, and 11.01×10⁹ Jones for a film doping density of 6.7×10¹⁸ cm^-3 of Ag₂Se CQDs.

The study uncovers the role of delicate interplay between spatial dispersion of impurity and Gaussian white noise on a few electrical properties of the doped GaAs quantum dot (QD). The electrical properties involve static dipole polarizability (SDP), dynamic dipole polarizability (DDP), quadrupole oscillator strength (QOS) and static quadrupole polarizability (SQP). The interplay between noise and the impurity spread depends on the pathway (additive/multiplicative) by which noise is applied. It has been found that, a gradual modulation of impurity spread, in conjunction with the mode of entry of noise, can effectively regulate the above electrical properties.

The present work examines the experimental electrical conductivities as a function of temperature for a variety of ionic liquids near room temperature. Three analytic models are used to describe them, the simple Arrhenius equation, the Vogel-Tamman-Fulcher equation and a novel semi-empirical modified form based on precedents for electrolyte solutions. Patterns are determined that relate the model that best describes the experimental conductivity of a given ionic liquid and its specific chemical structure.