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Motivated by the successful synthesis of 2D C2F diamanes [Bakharev, P.V. et al., Nat. Nanotechnol. 15, 59-66 (2020)], we have systematically investigated the structural stability, in-plane mechanical, optoelectronic, photocatalytic, piezoelectric, and thermoelectric properties of non-Janus and Janus diamanes monolayers named as C2H, C2F, C2Cl, C4HF, C4HCl and C4FCl. The structural stability is confirmed by cohesive energy, phonon dispersion spectra, and mechanical properties. The electronic properties has been calculated by HSE06 functional and the band gap are found to be 3.85, 5.64, 2.32, 4.16, 0.73 and 1.91 eV for C-2H, C2F, C2Cl, C4HF, C4HCl and C4FCl, respectively. The hydrogen-containing non-Janus and Janus diamanes monolayers have a higher negative Poisson's ratio (NPR) and therefore are good auxetic materials. From the Poisson's ratio and Young's modulus of each configuration of non-Janus and Janus diamanes monolayer, anisotropic behavior was displayed. From the optical properties calculations, the refractive index values are around 1.5, which means that it will be a transparent monolayered materials. Also, C2Cl, C4HCl and C4FCl monolayers displayed high absorption spectra with an order of 105 cm(-1) in the visible region, which shows great applications in optoelectronic devices. Additionally, the valence and conduction band-edge positions of 2D Janus and non-Janus diamanes of C2H, C2F, and C2Cl and C4HF monolayers have to straddle the redox potentials of water. It means that the photogenerated electrons and holes are sufficient to drive the overall water splitting. Whereas non-Janus diamanes C4HCl, and C4FCl monolayers displayed only water oxidation. The investigated in-plane piezoelectric coefficient has larger in non-Janus diamanes C4HF, C4HCl, and C4FCl monolayers. Therefore, it is very useful in the field of piezoelectric applications. From the thermoelectric properties, the non-Janus and Janus diamanes monolayers have great thermoelectric efficiency and were found to be 10.52 and 10.63% for C2H and C2F, respectively. Our results demonstrate the new class of 2D carbon-based monolayers has good auxetic materials as well as a wide range of applications in optoelectronics, piezoelectric, and thermoelectric fields. (C)& nbsp;2022 The Authors. Published by Elsevier Ltd.& nbsp

Hydrogen production via solar light-driven water dissociation has been regarded as an artificial and effective process to overcome the environmental problem as well as solving the current energy crisis. In this regard, numerous works have mainly been devoted to developing the appropriate photocatalyst which satisfies the conditions for water splitting and understanding the photocatalysis process. In this study, we propose for the first time the potential application of the two-dimensional Janus aluminum oxysulfide Al2OS as an efficient photocatalyst material for hydrogen-production H-2 through the first-principles calculations. Janus Al2OS monolayer has been designed from the parental binary aluminum sulfide AlS by substituting one sub-layer of sulfide atoms (S) to oxygen atoms (O). The electronic properties of the pristine AlS and the derived Janus Al2OS were computed using GGA-PBE and HSE06 functionals. According to the band structure, AlS monolayer shows a semiconductor behavior with an indirect bandgap of 2.14 eV whereas, the Janus Al2OS exhibits a direct bandgap of 1.579 eV. Motivated by the desirable bandgap of the Janus Al2OS, the absorption-coefficient of Janus Al2OS shows strong visible light harvesting compared to the parental AlS. Furthermore, the photocatalytic performance of Al2OS has been investigated. Our calculations demonstrate that the band edge position of Al2OS is suitable for the hydrogen evolution reaction (HER). More importantly, based on the reaction coordinate, it was found that the Gibbs free-energy Delta G(H*) of Al2OS is 0.97 eV which is smaller than of the two-dimensional Janus Ga2XY (X, Y = S, Se, Te with X not equal Y) reported recently. Moreover, this value decreases from 0.97 eV to 0.69 eV under 0.5 V/angstrom of an external electrical field. Our results indicate that Janus Al2OS fulfills the fundamental requirements for efficient photo-catalyst under visible light and provides new guidance for hydrogen-production via water splitting.

Promising flexible electrochemical energy storage systems (EESSs) are currently drawing considerable attention for their tremendous prospective end-use in portable self-powered electronic devices, including roll-up displays, and "smart "garments outfitted with piezoelectric patches to harvest energy from body movement. However, the lack of suitable battery electrodes that provides a specific electrochemical performance has made further development of these technologies challenging. Two-dimensional (2D) lightweight and flexible materials with outstanding physical and chemical properties, including mechanical strengths, hydrophilic surfaces, high surface metal diffusivity, and good conductivity, have been identified as a potential prospect for battery electrodes. In this study, taking a new 2D boron nitride allotrope, namely 2D orthorhombic diboron dinitride monolayer (o-B2N2) as representatives, we systematically explored several influencing factors, including electronic, mechanical, and their electrochemical properties (e.g., binding strength, ionic mobility, equilibrium voltage, and theoretical capacity). Considering potential charge-transfer polarization, we employed a charged electrode model to simulate ionic mobility and found ionic mobility has a unique dependence on the surface atomic configuration influenced by bond length, valence electron number, electrical conductivity, excellent ionic mobility, low equilibrium voltage with excellent stability, good flexibility, and extremely superior theoretical capacity, up to 8.7 times higher than that of widely commercialized graphite (3239.74 mAh g(-1) Vs 372 mAh g(-1)) in case of Li-ion batteries and 2159.83 mAh g(-1) in case of Na-ion batteries, indicating that the new predicted 2D o-B2N2 monolayer possess the capability to be ideal flexible anode materials for Lithium and Sodium-ion battery. Our finding provides valuable insights for experimental explorations of flexible anode candidates based on 2D o-B2N2 monolayer.

In the presence of the crystal field D/JCore and the external magnetic field h/JCore, using the Monte Carlo (MC) simulation based on the heat bath algorithm and the effective field theory (EFT), the triangular mixed spin nanowire model consisting of a spin-(1/2) core which is encircled by a spin-1 ferrimagnetic surface shell is studied. We have studied the special effects of the core surface and crystal field on the critical and compensation temperatures. Several properties, such as the magnetization, hysteresis behaviors, coercive field, and remanent magnetizations are studied. For the appropriate values of the system parameters, the compensation point and multi-loops are found PACS 05.50. + q; 77.80. Bh.

In this article, we investigate the magnetic and electronic properties of GaN doped with simple and double impurities utilizing Ab initio and Monte Carlo studies. We have predicted that (Ga, Cr)N and (Ga, Cr, V)N compounds exhibit ferromagnetic- and halfmetallic-behavior with 100% spin polarization at the Fermi level. Moreover, we have found that Ga1−xCrxN and Ga1−2xCrxVxN (x = 0.04, 0.05 and 0.06) show a second order ferromagnetic transition and that their Tc is above room temperature. These predictions make (Ga, Cr)N and (Ga, Cr, V)N compounds strong candidates for spintronic technologies.

International audience; We report the impact of an external electric field on the energy spectrum of an exciton inside a spherical shaped GaN/AlN core/shell nanodot. The modulation of the confined exciton lowest state energy by the nanodot size is also treated. Our theoretical approach, based on a variational calculation, predicts a remarkable decrease in the exciton's energy when the electric field is switched on. Furthermore, our investigation shows that for a fixed nanodot size, the energy redshift is a unique function of the external electric field strength. On the other hand, it was observed that as the nanodot size increases the lowest exciton energy decreases and vice versa.

Using the dynamicMonte Carlo (DMC) simulation, the dynamic magnetocaloric effect of a ferrimagnetic C70 Fullerene-like structure is studied within the dynamic Ising model under of a magnetic (h(t)) field. The influences of the amplitude (h 0) and the frequency (ω) of the h(t) magnetic field and bias field (hb) on the thermal behavior of the dynamic order parameter and the dynamic magnetocaloric properties (the dynamic isothermal Δ S iso ( T , h ( t ) ) entropy variation and the dynamic Δ T ad ( T , h ( t ) ) adiabatic variation of temperature), the dynamic specific heat, the dynamic entropy and as well as the dynamic refrigerant capacity (RC(t)) ferrimagnetic C70 Fullerene-like structure are studied. Our results may be a reference for future experiment and theoretical studies of the nano-clusters.

On the basis of spin density functional calculation, the electronic and magnetic properties of ZnSe doped with double impurities Zn1-2xFexCoxSe (x = 0.05) are studied using the Korringa-Kohn-Rostoker coherent potential approximation (KKR-CPA) method within the local density approximation (LDA). The half-metallic ferromagnetic nature of (Fe, Co) doped ZnSe is investigated. Therefore the electronic structure and magnetic properties of Zn1-2xFexCoxSe exhibit a half-metallic ferromagnetic character; the stability of ferromagnetic (FM) compared to the disorder local moment (DLM) has been discussed. Our calculation is supported by Monte Carlo simulations (MCS) based on the heat bath algorithm. We have examined the effects of system size L on magnetization, specific heat and magnetic susceptibility. The spin density functional calculation results are in good agreement with the literature, especially for 5% of (Co, Fe) each, which gives the most interesting results.

Using the 1st principle calculations founded on Density Functional Theory (DFT), we examined the strain effect of band gap (BG) and electrical property (EP) of Siligraphene (g-SiC7) under biaxial strains (Compressive and tensile) using Generalized Gradient Approximation (GGA). We found that the BG of g-SiC7 was decreasing as function of the strain and we remarked that the electrical conductivity of g-SiC7 under biaxial strains become important of 6% for tension effect. For the compressive, we obtained an increase for all compressive applying, but we remarked the higher and lower values are successively -2% and -6%. Last not least, we deduced that it's possible to increase the electrical conductivity of g-SiC7. Also, this material can be used in solar cell applications and for photo-voltaic (PV) applications as a light donor material.

Nowadays, secondary batteries based on sodium (Na), potassium (K), and magnesium (Mg) stimulate curiosity as eventually high-availability, nontoxic, and eco-friendly alternatives of lithium-ion batteries (LIBs). Against this background, a spate of studies has been carried out over the past few years on anode materials suitable for post-lithium-ion battery (PLIBs), in particular sodium-, potassium- and magnesium-ion batteries. Here, we have consistently studied the efficiency of a 2D alpha-phase arsenic phosphorus (alpha-AsP) as anodes through density functional theory (DFT) basin-hopping Monte Carlo algorithm (BHMC) and ab initio molecular dynamics (AIMD) calculations. Our findings show that alpha-AsP is an optimal anode material with very high stabilities, high binding strength, intrinsic metallic characteristic after (Na/K/Mg) adsorption, theoretical specific capacity, and ultralow ion diffusion barriers. The ultralow energy barriers are found to be 0.066 eV (Na), 0.043 eV (K), and 0.058 eV (Mg), inferior to that of the widely investigated MXene materials. During the charging process, a wide (Na+/K+/Mg2+) concentration storage from which a high specific capacity of 759.24/506.16/253.08 mAh/g for Na/K/Mg ions was achieved with average operating voltages of 0.84, 0.93, and 0.52 V, respectively. The above results provide valuable insights for the experimental setup of outstanding anode material for post-Li-ion battery.

Development of high capacity anode materials is one of the essential strategies for next-generation high-performance Li/Na-ion batteries. Rational design, using density functional theory, can expedite the discovery of these anode materials. Here, we propose a new anode material, germanium carbide, g-GeC, for Li/Na-ion batteries. Our results show that g-GeC possesses both benefits of the high stability of graphene and the strong interaction between Li/Na and germanene. The single-layer germanium carbide, g-GeC, can be lithiated/sodiated on both sides yielding Li2GeC and Na2GeC with a storage capacity as high as 633 mA h/g. Besides germagraphene's 2D honeycomb structure, fast charge transfer, and high (Li/Na)-ion diffusion and negligible volume change further enhance the anode performance. These findings provide valuable insights into the electronic characteristics of newly predicted 2D g-GeC nanomaterial as a promising anode for (Li/Na)-ion batteries.

The present work systematically investigates the structural, electronic, and optical properties of a MoS2/Si2BN heterostructure based on first-principles calculations. Firstly, the charge transport and optoelectronic properties of MoS2and Si2BN heterostructures are computed in detail. We observed that the positions of the valence and conduction band edges of MoS2and Si2BN change with the Fermi level and form a Schottky contact heterostructure with superior optical absorption spectra. Furthermore, the charge density difference profile and Bader charge analysis indicated that the internal electric field would facilitate the separation of electron-hole (e−/h+) pairs at the MoS2/Si2BN interface and restrain the carrier recombination. This work provides an insightful understanding about the physical mechanism for the better photocatalytic performance of this new material system and offers adequate instructions for fabricating superior Si2BN-based heterostructure photocatalysts.

The optical characteristics of a bound electron-hole quasiparticle inside a GaSb-capped InSb nanodot were investigated using a combination between a density-matrix approach and variational calculations. Our theoretical model considers the electric permittivity mismatch between the core and shell materials via the self-energy term obtained by the means of an image charge approach. Furthermore, the core-to-shell conduction and valence band offsets were modeled by finite-depth confinement potentials. To elucidate the impact of the nanoheterodot spatial parameters on the confined exciton optical properties, we have investigated the change of the refractive index, the optical absorption coefficient, and the 1p–1s exciton transition energy with respect to the nanodot shape. Our numerical results exhibit the great potential for the improvement of the exciton optical properties by tailoring the nanodot size. It was also obtained that, for a fixed core radius, the resonance peak position of the optical absorption coefficient was still constant after a certain shell thickness value. Otherwise, decreasing the shell thickness leads to blue-shifting the 1p–1s transition energy.

In this work, the mixed spin Ising nanowire model consisting of a spin-1 ferromagnetic core, which is surrounded by a spin-1/2 ferromagnetic surface shell is studied in the presence of magnetic and crystal fields using of the Monte Carlo (MC) Simulations based on the heat bath algorithm. We assume that the exchange interaction between two nearest-neighbor spins at the surface shell and the core is antiferromagnetic. We have examined the effects of the surface and the crystal field on the critical and compensation temperatures. The thermodynamic properties, the hysteresis behaviors are also studied. For appropriate values of the system parameters, the compensation point and multi-loops are found.

The impact of an external electric field on the binding energy of a single donor impurity was examined within the effective-mass approach by deploying a variational calculation. The discontinuity of the permittivity, ɛr, and of the particle effective mass, m i * r , at the nanosystem boundaries was considered. Using the image charge approach, the impact of the surrounding medium on the shallow donor energy spectrum was also taken into account. Our theoretical investigation shows that, for zero electric field and when the shell thickness is taken constant, the increase of the core material size leads to decrease the single donor correlation energy. Further, for a fixed core material size the energy decreases quickly when the shell thickness moves from 0 to 1 nm, while it decreases very slowly when the shell thickness is ranged between 1 nm and 4 nm. On the other hand, we have established that when we turn on an external electric field, the probability density of confined particles tends to move towards the nanodot border which naturally shifts the energy spectrum to lower energies (redshift). It was also obtained that the donor Stark shift depends not only on the nanodot size, but also on the surrounding medium.

The recombination energy of isolated neutral exciton and that of isolated negatively charged exciton inside a type-II core/shell spherical quantum dot are studied. Our investigation considers the charge-carriers effective mass discontinuity at the surface contact between the core and shell materials. Although our model omits the effect of the surface polarization, the dielectric-constant mismatch at the nanodot boundaries was taken into account. In order to achieve the exciton and negative trion energies, we proceed by a variational calculation in the framework of the envelope approximation. Our results reveal a strong correlation between the nanodot morphology and the energy spectrum of the neutral and negatively charged exciton.

In this theoretical study, based on the density functional theory, we investigate the electronic, optical and thermoelectric properties of SiGeC4 nanosheet, within the framework of mBJ-GGA approximation (modified Becke–Johnson generalized gradient approximation). The calculated results indicate that the two-dimensional SiGeC4 compound is energetically, dynamically, thermally and mechanically stable in the pentagonal structure and shows semiconductor character with indirect and moderate bandgap. Also, it is found that this two-dimensional system presents high absorption and low reflectivity as well as high photoconductivity in the visible range. Furthermore, it is shown that the studied compound exhibits good thermoelectric performance with high electrical conductivity and Seebeck coefficient. These results render the two-dimensional pentagonal SiGeC4 nanosheet as strong absorber layer candidate in the next generation of photovoltaic devices.

The massive consumption of traditional fossil fuel like oil, coal and natural gas has led to serious environmental issues, which drove the search for cleaner renewable energy sources. One such option is photocatalytic water splitting that has attracted much attention as a viable process for the large scale production of hydrogen as a renewable fuel. Within this perspective, we methodically studied the structural, optoelectronic, and photocatalytic properties of two-dimensional aluminum monochalcogenide monolayers with the chemical formula AlX (X = O, S, Se, and Te) based on the framework of Density Functional Theory (DFT). All considered structures are full relaxed and their thermodynamic stabilities are confirmed by computing the phonon spectrum and Ab Initio Molecular Dynamics (AIMD) simulations. The electronic characteristics are also performed on the basis of both exchange correlation functional GGA-PBE and HSE06 in order to obtain the accurate electronic band gap. According to our calculations, all the four monolayers posses indirect band gaps ranging between 1.937 and 2.46 eV. Furthermore, based on desirable electronic band gaps, the optical performance features were further explored including complex refractive index, absorption coefficient and energy loss function by means of the complex dielectric function. It is found that all the four materials present a high absorption coefficient in the visible and Ultra-Violet regions. Finally, the band edge positions of our monolayers straddle the reduction potential of H 2 and the oxidation potential H 2 O . Also, it was found that the Gibbs free energy of 2D AlO monolayer is 0.02 eV at certain applied external electric field and very close to ideal catalysts which suggest that the AlO monolayer is better candidate for hydrogen production. Our findings demonstrate that AlX monolayers are suitable materials for optoelectronics and hydrogen production via photocatalytic water splitting.

The effect of surface shell parameters on the hysteresis loop behaviors of a decorated Ising cubic nanotube, consisting of a ferromagnetic spin- 1 2 core which is interacting ferrimagnetically with a ferromagnetic spin-1 surface shell, is investigated, in the present work, within the effective-field theory with correlations based on the probability distribution technique. We have found that these parameters have a strong effect on the shape and the number of hysteresis loops and also on the coercive field and remanent magnetization behaviors. Indeed, triple, quintuple, septuple and nonuple hysteresis loop patterns have also been observed.

The behavior of the electron ground state and of the ground state binding energy of an on-center donor confined in a CdSe/ZnTe core/shell spherical nanodot was examined theoretically within the framework of the effective-mass approximation and using a variational calculation. The radial dependence of the dielectric constant and of the electron effective mass as well as the effect of the polarization charge were considered. Our results highlight the large impact of the magnetic field strength and the spatial parameters on the energy behavior for both the electron and the donor. Our study points out also the fact that the magnetic confinement may be eclipsed by the spatial confinement in heteronanostructures with small size and expected to be dominant in the opposite case.

Dielectric properties of Ising ferrielectric nanowires with spin-3/2 core and spin-5/2 shell structure are systematically studied by the use of the Monte Carlo simulation in the presence of the external longitudinal electric field. Special focus is given to the effects of the core and shell interactions, the interface coupling and the temperature on the core and shell polarizations, the specific heat, the compensations points, the susceptibility and hysteresis behaviors. Some characteristic behaviors are found, such as the existence of triple hysteresis loops for appropriate values of the system parameters affected by the antiferroelectric interface coupling constant and the temperature. The results are compared with those of recently published works and a qualitatively good agreement is found.

The binding energy of an exciton inside a CdSe/ZnTe core/shell spherical quantum dot was theoretically examined taking into account the dependence of the dielectric constant and charge carriers effective mass on radius, and using the envelope function approximation. Such a structure presents original optical and electronic properties because of the spatial separation of electrons and holes caused by the type-II alignment of energy states. The mean distance between the electron and hole was calculated variationally using a trial function taking into account the coulomb interaction between charge carriers. Our numerical results provide a description to the size dependence of the binding energy of an exciton inside a core/shell nanoheterostructure type-II. Indeed, by controlling the inner and outer radii, we can precisely control the energy spectrum of the exciton. (C) 2016 Elsevier Ltd. All rights reserved.

Using the dynamic quantum Monte Carlo simulation, the dynamic magnetocaloric effect of a ferromagnetic multilayer nanographene (MNG) is studied within the dynamic Ising model under the applied of a time-dependent oscillating ( h(t)) magnetic field. The influence of the amplitude h0 and the period τ of the h(t) and the transverse field Ω on the thermal behavior of the dynamic order parameter and the dynamic magnetocaloric properties (the dynamic isothermal Δ S T ( T , h ( t ) ) entropy change and the dynamic Δ T a d T , h ( t ) adiabatic change of temperature), the dynamic specific heat, the dynamic entropy and as well as the dynamic relative cooling power (RCP(t)) ferrimagnetic MNG are studied. Our predicted results may be a reference for future experiment and theoretical studies of the nanostructures .

In this work, we investigate the Magnetoelectronic properties of (V, Mn) codoped GaN using first principles calculations (FPCs) for the spintronic applications. We have obtained the ferromagnetic behavior in (Ga, V)N codoped with Mn atoms, which is believed to be caused by the double exchange mechanism. Moreover, it is observed that our system is halfmetallic at the Fermi level, with 100% spin polarization. The total magnetic moment of (V, Mn) codoped GaN is mainly originated from the V and Mn atoms, and the magnetic moment of V impurities rises with the concentration of V atoms while keeping constant that of the Mn atoms. In addition to that, the exchange coupling is obtained from FPCs and using the Ising model. The Monte Carlo method founded on the Heat Bath algorithm support our FPCs, by investigating the influence of the addition of Mn impurities to (Ga, V)N compound on the critical temperature T C MC , the magnetization per site M , the magnetic susceptibility χ and the specific heat C V . We have found that T C MC is above room temperature as well as the stability of the ferromagnetic state in (Ga, V)N becomes more important after the inclusion of the Manganese.

The EffectiveField Theory with correlations (EFT) based on the probability distribution is used to investigate the magnetic hysteresis behaviors of both hexagonal and square 2D nanoparticles consisting of a ferromagnetic spin-1/2 core and a ferromagnetic spin-l shell. The system parameters such as the ferrimagnetic exchange core/shell interaction, the surface shell exchange coupling and the reduced temperatureare examined on the magnetic hysteresis behaviors. Some interesting results have been found such as multiple hysteresis loop behaviors.

Two-dimensional Janus transition metal dichalcogenides structures have drawn increasing importance due to their remarkable properties for versatile applications in optoelectronic, photo-catalytic, thermo-electricity, piezoelectricity and spintronic. In this Paper, by employing the Ab-initio computations based on the density functional theory, the structural, electronic and optical properties of Janus MXO (M = Ti, Hf and Zr; X = S and Se) mono-layers are investigated utilizing full potential linearized augmented plane waves (FP-LAPW) method. The lattice parameters of the six Janus were computed, which are close to the previous theoretical results. The density of states and the electronic band structures were investigated for the first time using (GGA-PBE) approximation for the potential of the exchange and correlation. The optical parameters like complex dielectric function, refractive index, reflectivity, extinction and absorption coefficients of all Janus were performed. Our results reveal strong absorption coefficient and low reflectivity in the visible and ultraviolet regions, which make them candidates for opto-electronic and photovoltaic applications.

Using the effective-field theory EFT based on the probability distribution technique, the effect of the random crystal field on the magnetic properties of ferrimagnetic mixed Ising system with both spin-1 and spin-3/2 is investigated. The critical temperature is discussed as function of different strengths of the random crystal field and the exchange interactions. The phase diagrams are calculated numerically for a square lattice and the number of characteristic phenomena, such as the tricritical point are found. Our results are different to that reported in Souza et al. (Physica A 444, 589–600 2016).

Using the dynamic Monte Carlo simulation, the dynamic critical temperature of a ferromagnetic or ferrimagnetic double-walled nanotubes (DWNTs) is studied within the kinetic Ising model under the presence of a time-dependent oscillating external magnetic and crystal fields with mixed spins S (A) = 1 and S (B) = 3/2. The effects of the time-dependent oscillating external magnetic field, the period of the oscillating magnetic field, and the crystal field on the thermal behavior of the dynamic sub-lattice order parameters and the total dynamic order parameter, total dynamical magnetic susceptibility, dynamical specific heat, and dynamic hysteresis of a DWNTs are studied. Our theoretical predictions may be a reference for future experiment studies of the nanostructures.

The applied magnetic field dependencies of the surface shell, core and total magnetizations of a transverse spin -I Ising nanocube are investigated within the effective -field theory with correlations, based on the probability distribution technique, for both ferro- and antiferromagnetic exchange interactions. We have found that interfacial coupling has a strong effect on the shape and the number of hysteresis loops and also on the coercive field and remanent magnetization behaviors. Furthermore, when the temperature exceeds a critical one, the coercivities of the core, the surface shell and the system become zero. (C) 2016 Elsevier B.V. All rights reserved.

The effective-field theory with correlations based on the probability distribution technique is used to investigate the magnetic properties of a diluted Ising nanocube consisting of a ferromagnetic spin-1/2 core which is interacting antiferromagnetically with a ferromagnetic spin-1/2 surface shell. The effect of the concentration of magnetic atoms is examined. A number of interesting phenomena have been found such as the existence of the compensation temperature and triple hysteresis loops. (C) 2015 Elsevier B.V. All rights reserved.

The phase diagrams and magnetic hysteresis behavior of a spin-1/2 Ising core/shell nanoparticle are investigated by the use of the effective field theory with a probability distribution technique that accounts for the self-spin correlation functions. Nearest-neighbor pair interactions are incorporated between the Ising spins in the three parts of the nanoparticle that are core, core/shell and surface shell. The effects of the external magnetic field and core/shell exchange interaction on the thermal magnetization and susceptibility of the system are examined. (C) 2015 Elsevier B.V. All rights reserved.

In the present study, the combination of the First-principles density functional theory (DFT) calculations and Monte Carlo (MC) methods are investigated on the structural, magneto-electronic and magneto-caloric properties of the anti-perovskite carbides Mn3XC with X = Sn, Zn. Firstly, the electronic band structure and total/partial density of state of both Mn3SnC and Mn3ZnC are computed and compared to other theoretical and experimental works. Our results reveal that both Mn3SnC and Mn3ZnC structures exhibit a metallic behavior and the valence (VB) and conduction (CB) bands overlap considerably. Additionally, the magnetic and magneto-caloric properties including heat capacity (C), the entropy change (ΔS), adiabatic temperature (ΔT) and the refrigerant capacity (RC) were studied under the magnetic field ranging between 0 and 5 T for both anti-perovskites. Our findings suggest that both anti-perovskite carbide (Mn3SnC and Mn3ZnC) can act as an effective substrate for magnetic refrigeration.

In the current study, we explore theoretically electronic and optical properties of penta-SiC2 and -SiGeC4 monolayers based on ab initio computations and utilizing modified Becke–Johnson generalized gradient-approximation (mBJ-GGA) within the density functional theory. The calculated results show that both 2D penta-SiC2 and -SiGeC4 are structurally stable, according to their negative formation energy. Furthermore, we have found that the penta-SiC2 and -SiGeC4 semiconductors show indirect and moderate band gaps of 1.75 and 1.62 eV by employing mBJ-GGA functional, respectively. Also, these systems present sigma- and pi-bond between two nearest neighbor carbon atoms by overlapping sp2-sp2 and p-p orbitals, respectively, as well as an ionic bond between two nearest neighbor Si-C and Ge-C atoms. Additionally, we have shown that the considered compounds exhibit small reflectivity and high absorption peaks in visible region with the shift of absorption edge of 2D penta-SiGeC4 to the low energy visible region due to its small band gap compared to that of 2D penta-SiC2. These findings make both penta-SiC2 and -SiGeC4 monolayer semiconductors promising candidates for photovoltaic technology.

The current study is purposed to investigate the magnetic- and electronic-properties of Zn1-2xCrxTixSe and Zn1-2xCrxTixTe systems by means of Ab initio and Monte Carlo calculations. We have predicted that the two systems show ferromagnetic halfmetallic behavior with 100% spin polarization at the Fermi level and their ferromagnetic stability is attributed to the double exchange coupling. Our calculations suggest further that these compounds exhibit a 2nd order ferromagnetic transition with high Curie temperature. Thus, (Zn, Cr, Ti)Se and (Zn, Cr, Ti)Te compounds are strong candidates for spintronic devices, especially for magnetic random access memories (MRAM) based on the spin transfer torque.

In this paper, a theoretical study of the electronic, magnetic and electrical properties of double perovskite Mn2FeReO6 with a high Curie temperature so far in magnetic oxides was conducted, using several methods such as Ab-initio and Statistical Physics like Monte-Carlo Simulations (MCS). However, the first principles calculations showed a half-metallic behavior from the density of states and band structures calculation, using PBE + U (apply on the elements Mn, Fe, and Re respectively). The critical temperature obtained by MCS has a great similarity with the experimental results.

We have applied the first-principles calculations to investigate magnetoelectronic properties of Vanadium impurities co-doped (Cd, Cr)Te compound for spintronic devices. The ferromagnetic (FM) nature in (Cd, Cr)Te compound co-doped with V atoms has been found, and the mechanism responsible for this behavior has been considered to be the double exchange. Moreover, the Curie-temperature calculation reveals that the stability’s field of the FM-phase rises with rising both the concentration of Cr and V atoms above ambient temperature. This system presents the half-metallic character where its polarization of spin is total at the Fermi level, and its total magnetic moment is principally induced by Cr and V elements. The spin-orbit coupling (SOC) typically play an important role in the electronic structure calculations due to both the concentration of Cr and V impurities. In addition to that, our results have been confirmed by the calculation of magnetization and susceptibility using the Monte Carlo simulation.

The critical and hysteresis behaviors of a ferrielectric Blume–Capel nanowire are studied using the Ising model with mixed spins-( 1 2 , 1) in the presence of both an external longitudinal electric ( E z ) and crystal anisotropy ( D ) fields. We use the Monte Carlo simulations (MCs) to examine the influence of E z , D and the exchange interactions on the compensation and critical temperatures, the specific heat, the dielectric susceptibility and the internal energy of the system. Our theoretical predictions are in accordance with some experimental and theoretical results.

Using the Quantum Monte Carlo simulation (QMCS), the dynamic blocking temperature of a nanographene bilayer has been investigated within the framework of the Transverse Ising Model (TIM) with mixed spins, under the existence of the time-dependent oscillating longitudinal magnetic field (h(t) = h(b) + h(0)cos(omega t)) and the transverse field (Omega). The influence of the time-dependent oscillating longitudinal magnetic field, the period of magnetic field (tau) and the transverse field (Omega) on the thermal behavior of the total longitudinal and transverse dynamic order parameters, the total dynamic magnetic susceptibility and the dynamic hysteresis of the nano-graphene bilayer are also studied. As results, we remark the appearance of multiple hysteresis loops and the system exhibits the superparamagnetic behavior at the dynamic blocking temperature. (C) 2018 Elsevier B.V. All rights reserved.

We have investigated in the framework of the envelope function approximation and taking into account the dependence of the electron effective mass on radius the energy of an electron inside a ZnTe/CdSecore/shell spherical quantum dot. In order to make the problem more realistic, we describe the conduction band-edge alignment between core and shell materials by a finite height barrier. By applying the Ritz variational principle the effect of the electric field on the electronic states was also examined. Our numerical results show the opportunity to control the energy states position of the charge carriers inside our core/shell nanostructures by controlling the size (core radius, shell thickness) of the nanostructure and the strength of the external electric field. #CORE/SHELL MATERIALS #NANOSTRUCTURES #QUANTUM DOTS #ELECTRIC FIELD

The effects of longitudinal and transverse crystal-fields on the magnetic hysteresis behaviors of 2D spin-1 Ising nanoparticles are investigated, by using the effective-field theory based on the probability distribution technique with correlations. Nanoparticles with hexagonal or square lattice are studied. A number of characteristic phenomena such as triple and quadruple hysteresis loop behaviors have been observed for certain physical parameters, originating from the competitions among the core/shell exchange interaction, anisotropies, temperature and the longitudinal magnetic field. Finally, the obtained results are compared with some experimental and theoretical results.

Using the effective field theory with a probability distribution technique that accounts for the self-spin correlation function, the thermal and the magnetic properties of a single Ising nanopartic ...

In the present work, we have examined the influence of surface shell exchange coupling on the magnetic properties of a diluted ferromagnetic spin- 1 Ising nanocubic particle, by employing the effective-field theory with correlations based on the probability distribution technique. Some interesting results have been found such as, a tricritical point, a triple point, an isolated critical point, reentrant and even double reentrant phenomena, S-, R- and Q-type behaviors, as well as, both first-and second-order phase transitions as it is confirmed by the free energy. In addition, when the interactions are low between the surface shell sites, quadruple hysteresis loops can be seen in the system. (C) 2017 Elsevier B.V. All rights reserved.

International audience; We have reported the impact of the core and shell radii on the energy spectrum of centered shallow donor confined inside CdSe/ZnTe core/shell quantum dot and ZnTe/CdSe inverted core/shell quantum dot. The dielectric discontinuity between the nanosystems and their surrounding medium was considered. In order to examine the behavior of the donor binding energy as a function of the spatial parameters a variational approach within the framework of the effective-mass approximation was deployed. Our model shows that for a fixed shell radius the increase of the core radius value blue-shifts the binding energy of the donor inside inverted core/shell quantum dot only if the value of the core to shell radii ratio is between 0.9 and 1, otherwise it is red-shifted. By contrast, for core/shell quantum dot system the binding energy is red-shifted by increasing the core radius for a fixed nanostructure size and for all values of the core to shell radii ratio. We have also found that the donor binding energy values are more important in a core/shell nanodot than in an inverted core/shell quantum dot.