Narrow Results

A new all-$d$-metal full-Heusler alloy (Cd₂MnPd) was designed based on density functional theory. Its crystal structure, band structure, density of states, magnetism, and the possibility of martensitic transformation were studied. The calculated total energy shows that the most stable cubic structure of this alloy is the L2₁ type at ferromagnetic (FM) state, and the equilibrium lattice constant is 6.57Å. The band structure and density of states show that it is a FM metal with a total magnetic moment of 3.97${\mu }_B$, mainly originating from the Mn element. The results of the martensitic transformation investigation show that the martensitic phase has minimum energy when the c/a ratio is 1.35, and the absolute value of the energy difference ($\mathrm{\Delta }{E}_M$) between the martensitic and the austenitic phases is 0.07eV. This indicates that there is a high possibility that a stable martensitic phase exists. Furthermore, $\mathrm{\Delta }{E}_M$ can be tuned by uniform strain, and the absolute value of $\mathrm{\Delta }{E}_M$ increases as the volume increases in the range of $V_{\mathrm{\text{opt}}}\pm 3\%V_{\mathrm{\text{opt}}}$ ($V_{\mathrm{\text{opt}}}$ is the optimal volume, namely, the cubic volume under its equilibrium lattice). In conclusion, Cd₂MnPd may be a good candidate for ferromagnetic shape-memory alloys (FSMAs). We expect that our theoretical prediction can provide guidance for exploring valuable FSMAs experimentally.

We are attempting to study the properties of new materials based on Diamond-like semiconductors (DLS). Due to broad collection of useful properties, DLS are exciting materials to study. The novel substances Li₂MnGeS₄ and Li₂CoSnS₄ result from using a rational and guileless design approach that leads the discovery of DLSs with wide-ranging regions of optical transparency. So here, we have analyzed their applications in atomic devices and system called “optoelectronic” using the FP-APW method and mBJ method. The band gap value for Li₂MnGeS₄ is 2.911eV and Li₂CoSnS4 is 2.45eV. The present DLS materials confirm their semiconductor characters. The presence of iron and manganese in these compounds have generated magnetic properties that we explored by the calculation of magnetic moment and spin-densities maps.

A novel half-metallic family of materials, the multiple Dirac cones half-metals, has received considerable interest from researchers. Benefiting from its novel electronic structure, they are promising candidates for ultra-performance spintronic devices. In this paper, we propose a new half-metallic material, perovskite-type $R\stackrel{-}{3}c$ HoMnO₃, which possesses similar Dirac-like multiple linear band crosses. We investigated its electronic, magnetic and thermodynamic properties in detail on the basis of density functional theory. The excellent band structures are robust enough against spin-orbit coupling and electron and hole doping. Through calculations, we confirmed its multi-aspect stability. Based on the current study, we confirm that HoMnO₃ has potential for next-generation spintronic applications.

In this paper, we investigate the structural, electronic and magnetic properties of CoFeCrZ ($\mathrm{\text{Z}}=\mathrm{\text{P}}$, As,Sb) quaternary Heusler alloy, using the first-principles full potential linear muffin-tin orbital (FP-LMTO) method within the spin gradient generalized approximation (GGA) for the exchange and correlation potential. Our results demonstrate that in ferromagnetic phase, the all alloys CoFeCrZ are stable in type-1 configuration and are half-metallic ferromagnets (HMF) with gaps of 0.99eV, 0.57eV and 0.70Ev, respectively. The obtained negative formation energy shows that CoFeCrZ alloys have strong structural stability. The calculated total magnetic moment, $M_T$ for all alloys exhibit Slater-Pauling rule, $M_T=(N_V-24){\mu }_B$. At zero pressure, the three alloys shown 100% spin-polarization at Fermi–level $E_F$ with high Curie temperatures $Tc$. Our calculation indicate also that the half-metallicity and high magnetic moment of CoFeCrP, CoFeCrAs and CoFeCrSb are robust against the lattice compression (up to 7.80%, 5.40% and 11%, respectively). On the basis of these results, it is suggested that the CoFeCrZ Heusler could be suitable for spintronics devices applications.

In this work, the structural, electronic and optical properties of Si-doped barium chalcogenide [barium sulfide (BaS)] with different Si concentrations ($0\le x\le 0.25$) are investigated by the first-principles calculations based on the density functional theory (DFT). The band structures, charge densities and complex dielectric functions of the pure as well as Si-doped BaS were presented and analyzed in detail using TB-mBJ approach by WIEN2k package. It is found that silicon concentration can control the bandgap by reducing it to values around 1.4eV and 1.6eV for 12.5% and 6.25% of Si-doped BaS, respectively. The electron charge density indicates the ionic bonding between silicon and sulfur atoms due to the high electronegativity between them. In fact, the results show that the absorption peaks of Si-doped BaS are enhanced compared with pure BaS. These results suggest that the Ba${}_{1-x}$Si_xS original structure displays excellent physical properties thereby revealing that it is a promising material in advanced optoelectronic and solar cell applications.

This work presents ab initio study of the structural, electronic, magnetic and mechanical properties of Fe₂NiAl${}_{1-x}$Ga_x Heusler compounds with variable concentrations ($x=0$, $x=0.25$, $x=0.50$, $x=0.75$ and $x=1$) of Ga. Calculations have performed using the full-potential linearized augmented plane waves (FP-LAPW) method within generalized gradient approximation Perdew–Burke–Ernzerhof (GGA-PBE) formalism in order to describe the exchange–correlation potential. The obtained results showed that the equilibrium parameter values are in good agreement with the available experimental results. In the study of the electronic properties, band structure analysis indicated that all of our compounds have metallic behavior. The calculated total magnetic moments of our Heusler alloys are in line with the Slater–Pauling rule, and they agreed with the results of previous studies. For mechanical properties, shear modulus, Young’s modulus, elastic constants, Poisson’s ratio and shear anisotropy factor have studied. Their obtained values reveal that these compounds are mechanically and dynamically stable.

Double perovskites are usually strongly correlated electronic systems that offer many multifunctional properties and are most commonly formed in the monoclinic crystal phase. In this study, we used a first-principles DFT approach in studying the optical and magnetic aspects of Ba₂MMoO₆ ($\mathrm{\text{M}}=\mathrm{\text{Mn}}$, Fe) double perovskite structures in a new monoclinic phase in both their pure and oxygen-deficient form and compared it to their natural cubic phase. The structural parameters of our structures were consistent with the available experimental data of the similar Ca₂MMoO₆ compounds. The optical analysis suggests a high dielectric function for both compounds in their pure and defected state. The addition of defects increases the absorption of photons near the visible spectra. We also found the structures to be half-metallic, with a reduction of magnetic strength and half-metallic gaps when oxygen defects are added to the structure. These features suggest a possible application in the optoelectronics and spintronics industry, even when the crystal structures have oxygen vacancies.

We report on our results obtained on the physical properties of B_xIn_yGa${}_{1-x-y}$N quaternary alloys in the zinc-blende phase that are thoroughly considered by the linearized augmented plane wave method, with a full potential within density functional theory, for different concentrations $x$ and $y$ as employed in the Wien2k code. We calculated the structural properties, including lattice constant $a_0$ and the bulk modulus $B$. We computed as well the band structures, the dielectric constant and the refractive index of our quaternary alloys compounds. Finally, nonlinear dependence on the compositions $x$ and $y$ are investigated in-depth and still expecting for experimental confirmations. To the best of our knowledge, this is the first theoretical investigation of B_xIn_yGa${}_{1-x-y}$N alloy conducted to date.

This research work studies the structural, electronic and magnetic properties of Ge${}_{1\text{\_}x}$Ti_xTe (for $x=0.25$, 0.50, 0.75, 1) compounds in rock-salt structure based on first-principles spin-polarized density functional theory. As it is implemented in WIEN2k code, the full-potential augmented plane-wave method was used in the investigation. To evaluate the structural properties of compounds, the exchange-correlation term is estimated using PBE-GGA approximation. For the other properties such as the electronic structures, densities of states and local moments, the generalized gradient approximation PBE-$\mathrm{\text{GGA}}+U$ is used. The analysis of spin-polarized density of states has shown the half-metallic ferromagnetic character when $x=0.50$ and 0.75; while at $x=0.25$, we obtained near half-metallic behavior. In order to validate the effects resulting from exchange splitting process, we calculated the exchange constants $N_{0\alpha }$ and $N_{0\beta }$. For Ti atomics sites, the value of total magnetic moment has been estimated equal to $2{\mu }_B$ in all studied compounds. We have found that the local magnetic moment of Ti is reduced and small local magnetic moments on nonmagnetic atomics sites of Ge and Te were created by the p-d hybridization effect.

In this paper, the structural, electronic, magnetic, and half-metallic properties of full-Heusler alloys Mn₂ZrX ($\mathrm{\text{X}}=\mathrm{\text{As}}$, Bi) in the Hg₂CuTi-type structure have been studied by using the first-principles-based density functional theory (DFT) with the full-potential linearized augmented plane-wave (FP-LAPW) method. Mn₂ZrX ($\mathrm{\text{X}}=\mathrm{\text{As}}$, Bi) compounds are found to be half-metallic ferrimagnets. The calculated total magnetic moments of the Mn₂ZrX ($\mathrm{\text{X}}=\mathrm{\text{As}}$, Bi) alloys are estimated at 01${\mu }_B$ according to the Slater–Pauling rule of $M_{\mathrm{\text{tot}}}=$ ($Z_{\mathrm{\text{tot}}}$–24) ${\mu }_B$. It was discovered that Mn₂ZrAs and Mn₂ZrBi maintained their half-metallicity for a lattice constant interval of 5.72 to 6.26 Å and 6.33 to 6.62 Å, respectively, and present a maximum degree of spin polarization at the Fermi level. In addition, the predicted formation energy and elastic parameters show that these materials are mechanically stable. All of these results indicate that these new Mn₂-based heusler alloys are able to be the candidates for spintronic applications.

In this research, we investigate the impact of strain on the optoelectronic and thermoelectric properties of the NaGeI₃ perovskite by employing a combination of density functional theory (DFT) and Boltzmann transport theory. Initially, we examine the NaGeI₃ material’s structural, electronic, and optical properties using the generalized gradient approximation (GGA). The results reveal that this material proves the behavior of a semiconductor with a p-type character and possesses interesting optical properties. Furthermore, we outline the thermoelectric properties of the material, including the Seebeck coefficient, the electrical and thermal conductivities, the figure of merit (ZT), and the power factor (PF). Our investigations indicate that the Seebeck coefficient exhibits positive and increasing values with the application of strain. This confirms the p-type semiconductor behavior observed in the studied material. Additionally, the NaGeI₃ compound demonstrates significantly high values of the ZT when compared with the existing thermoelectric materials, both at room and high-temperature values. This suggests that the NaGeI₃ compound stands as a promising potential candidate for optoelectronic and/or thermoelectric applications.

MXenes are a family of two-dimensional materials that could be attractive for use as electrodes in lithium batteries due to their high specific capacity. For this purpose, it is necessary to evaluate magnitudes such as the lithium adsorption energy and the magnitude of the open-circuit voltage for different lithium concentrations. In this paper, we show through first-principles calculations that in a V₂C monolayer, we must consider the high correlation between the electrons belonging to vanadium to obtain correct results of these quantities. We include this correlation employing the Hubbard coupling parameter obtained by a linear response method. We found that the system is antiferromagnetic and that the quantities studied depend on the magnetic phase considered. Indirectly, experimental results could validate the theoretical value of the Hubbard parameter.