The critical behavior and its relation to the magnetocaloric effect in the amorphous Eu80Au20 alloy prepared by the melt-quenching technique are studied in detail. At 4.2 K, the magnetic moment is found to be 6.6 µB/Eu2+ ion (at µ0H = 4 T), which is smaller than the theoretical value of 7 µB/Eu2+ ion, indicating a misalignment of moments. The Curie-Weiss temperature (θP) and experimental effective magnetic moment ( μ_eff^exp) are deduced from the Curie-Weiss law. The magnetic transition from the ferromagnetic state to the paramagnetic state was found to be a second-order magnetic phase transition. The critical exponents (CEs) in amorphous Eu80Au20 alloy are explored around its Curie temperature (TC) and are examined using a variety of techniques, including the modified Arrott plot, the Widom scaling relation, critical isotherm analysis, and the Kouvel-Fisher method. The computed values of the CEs agreed with those predicted by the mean-field approach. Based on these results, one may be able to conclude that the ferromagnetic exchange interaction is the long-range type.

The thermoelectric performance of the materials, which is of great interest for the waste heat recovery and solid-state cooling, is determined by figure of merit or the ZT for the two-dimensional honeycomb lattices GeC, SnC and SiC. Using the first principles calculations based on the GGA and HSE approximation, it is found that that SiC and SnC are indirect semiconductors, unlike GeC which exhibits a direct band gap. Furthermore, calculations employing semi-classical Boltzmann transport theory reveal that the thermoelectric performance of these 2D compounds is improved with respect to their graphene, silicene and germanene counterparts. At 700 K, the highest figure of merit (ZT) is 0.78 and 0.46 for GeC and SiC respectively, while it reaches the great value of 2.08 for SnC material that exhibits the lowest thermal conductivity. Our findings assess the potential of CX {X = Si,Ge,Sn} compounds as suitable thermoelectric materials at the temperature gradient from 100 to 700 K.

The thin films Fe doped copper sulphide Cu1−xFexS (CFS) (x = 0.01, 0.03, 0.05, and 0.07) were elaborated by spray pyrolysis deposition technique. The characterization by XRD and SEM of the thin films shows a Covellite CuS single phase without formation of other phases. The structure is a simple hexagonal with unit cell dimension, a = b = 3.79 Å and c = 16.34 Å. The Analysis of the UV–Vis spectra reveals that the energy band gap has been decreased from 2.47 to 1.98 eV with the increase of Fe concentration. The absorption coefficients of CFS films have increased from 1.155 × 105 to 1.712 × 105 cm−1. It has demonstrated that a right band gap with a right band edge alignment at a pH value for Fe-doped CFS can boost the material application as a photocatalyst for the visible light. According to this study, CFS (0.07) thin films for a pH = 3 solutions is a promising material for photocatalysis application for water splitting to hydrogen-oxygen production. Nevertheless, we demonstrate that the formation of straddling gap heterostructure for CuS and CFS for a pH solution between 7 and 8 induces the production of oxygen and hydrogen.

In this paper, a combination of DFT study and Monte Carlo (MC) simulations has been performed on Gd compound which undergoes a second–order phase transition from ferromagnetic state to paramagnetic one. For this single material, the temperature-dependent total magnetization and magnetic susceptibility have been calculated and are revealed that the Curie temperature is acceptable concurrence with the experimental value. Furthermore, it was showed that under an external magnetic field of 2 Tesla (T), MCE of Gd compound around its Curie point in regard to the maximum value of magnetic entropy change ( − Δ S m a g M a x ), agrees well with the experimental one. Besides, the Relative Cooling Power (RCP) values are found to be 34.37, 69.18, 90.74 and 128 J.kg−1 under different magnetic fields of 0.5, 1.0, 1.5 and 2T, respectively. All findings which are presented here indicate that DFT calculations and Monte Carlo simulations can be efficiently used to predict the magnetic and magnetocaloric features of Gd and related alloys.

The present study is carried out for investigating the half-metallic ferromagnetic behavior of Cr and Fe doped and co-doped GaN, respectively. To this end, ab-initio calculations using the Korringa-Kohn-Rostoker Green's function method coupled with the coherent potential approximation have been employed. In the background to make the study more useful, the first-principles computations were added and merged to the mean-field approximation and the Monte-Carlo simulation for the co-doped compound. Several variations were perceived in the results as in the bandgap energy, the energetic location of the transition-metal 3d band and the X-ray absorption spectra. Besides, the stability of the system between the ferromagnetic and the spin-glass states is studied. Finally, we have integrated as input parameters in the classical Ising model by Monte-Carlo simulation, the exchange interactions obtained from ab-initio calculation, in order to confirm the half-metallic ferromagnetic states with high Néel temperature.

The purpose of this paper is to investigate mass and heat transfer in the process of film condensation of vapor-air mixture for non-cryogenic fluids flow in a small vertical tube. A two-phase mathematical model is developed to model the mixture and liquid film. The governing equations for mixture and liquid-film have been resolved using a numerical method. Furthermore, this phenomenon analyzed is linked to a steady-state. Therefore, the development of numerical codes allows us to investigate the effect of implicated parameters on this phenomenon. Ethanol and methanol as non-cryogenic typical working fluids are realized for a good understanding of the heat and mass transfer mechanism during condensation. In this way, several effects of influencing parameters were examined. The predicted results showed a good agreement with experimental data.

In this paper, we consider the electronic and magnetic proprieties of five rare-earths (RE = Pr, Pm, Sm, Dy, and Tm)-doped Tin (IV) oxide semiconductor Sn1 − xRExO2 (x = 0.10) in the rutile structure. The presence of the 4f orbitals in our structures pushes us to choose the local density approximation with Self-interaction-corrected (LDA-SIC) to improve the obtained results. We also discuss the critical temperature retrieved from the study the total magnetizations and the susceptibilities using Monte Carlo simulations for each rare-earth element used.

Layered charge-density-wave (CDW) materials exhibit a lot of interesting aspects for their potential in a variety of device applications. So, a good understanding of their properties may enable the better development of new devices based on them. We address in this paper a study of the dynamic properties of CDW two-dimension electronic crystal in the presence of weak interchain interaction. This study was done through numerical experiments based on the generalized Fukuyama–Lee–Rice (FLR) model. One of the results of this Letter showed that the time-dependent spatially averaged velocity exhibits the steady-state regime characterized by a series of quasi-periodic fluctuations. Moreover, it was found that the increase in the weak interchain interaction effect reduces the NBN amplitude and normalized excess conductivity. All findings accessed here were discussed in the context of the inhomogeneous nature of CDW’s dynamics, damping mechanism as well as the attenuation of phase solitons which are nucleated when the CDW’s slide.

Herein, teh first TEMPprincipal calculations and Monte Carlo Simulation (MCS) were performed to investigate teh magnetic and magneto-caloric properties of PrSi compound. Teh partial magnetic moment of Pr (m(Pr)), and teh exchange interactions parameters (J(1), J(2)) are found to be m(Pr )= 2.8 mu(B), J(1) = 1.707 meV and J(2) = 1.312 meV, respectively. Through teh MCS, it was found dat teh Curie temperature value (T (c)) from ferromagnetic to paramagnetic state is T (c) = 55 K, which is in good agreement wif teh experimental value which is 54 K. Moreover, it was established dat a slight increase in teh applied magnetic field leads to a high increase in teh magnetic entropy from 4.4 J/kg K for h = 1 T to 13.7J/kg K for h=5 T. Furthermore, teh values of adiabatic temperature change and relative cooling power (RCP) obtained for h = 5 T were found to be 3.6 K and 550 J/kg, respectively.

In the present work, Sr-doped ZnO (SZO) thin films were grown on heated glass substrates (250 °C) by the ultrasonic spray technique. The effect of strontium concentration on the structural and physical characteristics was studied. The molar ratio of strontium in the ultrasonically sprayed solution was varied from 0 to 5 at.%. Several characterization techniques have been investigated to analyze the SZO thin films. The X-ray diffraction results showed that the SZO thin films exhibited the hexagonal wurtzite structure of ZnO with a preferential orientation along (002) plane. Scanning electron microscope indicated that the surface morphology of the SZO thin films changed with the increase in Sr concentration. No impurity was present in all the SZO films which was confirmed by the elemental composition analysis. Moreover, Fourier transform infrared spectroscopy showed the chemical bonding of zinc oxide (ZnO) and confirmed the incorporation of the dopant into the ZnO lattice. From the UV–Vis studies, it was found that the optical band gap decreased from 3.34 to 3.04 eV by increasing Sr doping concentration. Measurements of the Hall Effect indicated that all the elaborated samples exhibited n type conductivity. From all the films studied, SZO (1 at.%) was the most suitable for applications in optoelectronic devices, where a large figure of merit was required.

We report results regarding the temperature effect on dynamic properties of a 1D CDW system in the presence of normal carriers. It was showed that, for a given normal carriers concentration, the CDW phase profile fluctuations are attenuated by thermal fluctuations for the reason that the free-carrier relaxation process leads to a screening of the applied electrical field to depin the CDW. Further, the behavior of both the threshold field and nonlinear excess conductivity with respect to temperature were found to be non-monotonous. These findings are explained by the damping process and by generating CDW dislocation.

In this Letter, Equilibrium Molecular Dynamics (EMD) simulations were used to investigate the nanoparticle volume fraction-dependent thermal conductivity of nanofluids composed of one-dimensional (1-D) network of interconnected gold nanoparticles (IAuNPs) within the Green–Kubo formula. Thermal conductivities of nanofluids containing spherical AuNPs were also studied for comparison. The results showed that the 1D network shape of IAuNPs improves the nanofluid thermal conductivity better than the spherical shape of AuNP. The mechanism responsible for this finding is discussed using the Mean-Square-Displacement (MSD) analysis and the Radial-Distribution-Function (RDF).

In the present letter, the numerical study on the dynamic properties of incommensurate charge-density-waves (CDW's) in the two-dimensional (2-D) system has been performed by means of the generalized model of Fukuyama-Lee-Rice (FLR). The results showed that the weak interchain interaction effect affects the threshold field and the nonlinear excess current transported by the sliding CDW's as well as the associated nonlinear excess conductivity. All findings obtained in this work are discussed in the context of damping mechanisms of the collective motion of CDW-condensates.

Structural analysis and surface lattice contraction of gold nanoparticles (AuNPs) bounded by low-index {1 0 0}, {1 1 0}and {1 1 1} facets, with sizes in the range of 43-28897 atoms (Diameters from 1 to 10 nm) were investigated within the framework of Molecular Statics (MS) simulations based on the Embedded Atom Method (EAM) potential model. The present study provides insight into the size-dependent structural properties in AuNPs. All the numerical findings obtained in this Letter were compared with the available theoretical and experimental results.

Understanding how the temperature affects in a wide range of quasi-one-dimensional conductors is one of the most significant scientific challenges in solid state physics. In this paper, the temperature-dependent charge density wave (CDW) dynamic properties of a one-dimensional conductor in the weak pinning limit was studied within the temperature limit of 0-1 K. To do so, a model which incorporates the essential feature of the Fukuyama-Lee-Rice (FLR) model of CDW's has been considered The simulation results have shown that the threshold field and nonlinear excess current exhibit non-monotonous behavior as a function of the temperature. The mechanisms leading to this finding is interpreted in terms of several phenomena like thermal softening, damping mechanisms of the collective mode as well as the generation of the CDW dislocation. Besides, it was found that the CDW phase profile variations are more pronounced when the temperature increases. This finding was discussed in the context of thermal softening behavior.

In this Letter, the structural stability, local structure characterization and magnetic properties of iron nanoparticles (FeNPs) were investigated by using a combination of Molecular Statics (MS) and Monte Carlo (MC) simulations. To do so, six kinds of spherical-shaped FeNPs with diameters in the range of 3.14 to 5.42 nm have been considered. The coordination number distribution of FeNPs obtained from the data extracted by MS simulations was exploited for performing MC simulations on the familiar Ising model. The numerical findings obtained in the current study show that the structural and magnetic properties correlate with the size of the FeNP.

Using first principles calculations based on density functional theory, a computational investigation is carried out to explore the electronic band structures over a range of multilayer of MgH2 materials on SnO2 substrate. The results show that the band structure of magnesium hydride can be tuned by designing ultra thin layer devices that can affect the interatomic distances in a substrate -engineering approach, such a scheme can have marvelous applications for the design of new semiconductor materials and devices.

Achieving a higher heat transfer in nanofluids is one of the most important scientific challenges in order to reach a better efficiency in several sectors of technology. Here, the thermal conductivity enhancement of nanofluids composed of rod-shaped gold nanoparticles (AuNPs) compared to that of nanofluids with spherical-shaped AuNPs has been investigated by means of Equilibrium Molecular Dynamics (EMD) simulations combined with the hybrid pair potential option in a LAMMPS software which incorporate the Embedded-Atom-Method (EAM) potential and the 12–6 Lennard-Jones (LJ) one. The EAM potential was used to describe solid-solid interatomic interactions, while the interactions solid-liquid and liquid-liquid were modeled by employing the LJ potential. The simulation results illustrated that the suspension of the rod AuNP in base fluids is more effective in improving the effective thermal conductivity of nanofluids than that of the spherical AuNP. Mechanisms behind this finding are discussed using the Mean-Square-Displacement (MSD) and Radial-Distribution-Function (RDF). Several parameters like NP surface effect, solid-liquid interface and the enhanced mobility of liquid atoms in nanofluids were considered to explain the results.

Iron pyrite, FeS2 (FS) and the chalcopyrite copper iron sulphide CuxFe1-xS2 (CFS) thin films were synthesized using chemical spray pyrolysis (CSP) deposition technique. The effect of different Cu concentration (1, 3, 5 and 7 at.%) on growth of these films was investigated. The as-synthesized CFS thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet-visible (UV-Vis) spectroscopy. The XRD pattern of FS show a structured cubic phase with preferential orientation along (2 0 0) plane, and CFS crystallized in chalcopyrite (tetragonal) with preferential orientations along (1 1 2) plane with crystallite size 142-91 angstrom. Optical absorption data show that the band gap of spray deposited FS and CFS films is 0.920-0.558 eV and the absorption coefficients significantly modified with the increase of Cu concentration from 3.619 x 10(5) cm(-1) to 4.231 x 10(5) cm(-1). Furthermore, these results have been adopted in accordance with the first principles calculations of electronic structure.

The half-metallic ferromagnetic of Gallium nitride doped with double impuritiesGa1−2xMnxCoxN (x=3% and 6%) has been investigated by means of first principles investigation combined with Monte Carlo Simulation. The stability of the ferromagnetic state is investigated by comparing the total energies to the spin-glass state. The exchange interactions obtained from first principle calculations and used in a classical Ising model by a Monte Carlo approach resulted in half-metallic ferromagnetic states with high Neel temperature.