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This investigation delves into the adsorption characteristics of CO, NO, NO2, NH3, and O2 on two-dimensional (2D) Janus group-III materials, specifically Al2XY and B2XY. The examination covers adsorption energies and heights, diverse adsorption sites, and molecular orientations. Employing first-principles analysis, a comprehensive assessment of structural, electronic, and optical properties is conducted. The findings highlight NO2 as a prominent adsorbate, emphasizing the Te surface of 2D Al2STe and B2STe materials as particularly adept for NO2 detection, based on considerations of adsorption energy, height, and charge transfer. Additionally, the study underscores the heightened sensitivity of work function changes in the B2STe material. The adsorption properties of all gas molecules, except for NO2, on both materials were determined to be physical. Upon adsorption of the NO2 gas molecule onto the B2STe Janus material, it was observed that the material exhibited weak chemical adsorption behavior, which was confirmed by the adsorption energy, larger band gap change, electron localization function, work function changes and charge transfer from the material. This research provides valuable insights into the gas-sensing potential of 2D Janus materials. [ABSTRACT FROM AUTHOR]

Using the first-principles calculations based on density functional theory (DFT), the structural, elastic, electronic, and vibrational properties of LiAl have been explored within the generalized gradient approximation (GGA) using the Vienna ab initio simulation package (VASP). The results demonstrate that LiAl compound is stable in the NaTl-type structure (B32) at ambient pressure, which is in good agreement with the experimental results and there is a structural phase transition from NaTl-type structure (B32) to CsCl-type structure (B2) at around 22.2 GPa pressure value. The pressure effects on the elastic properties have been discussed and the elastic property calculation indicates that the elastic instability could provide a phase transition driving force according to the variations relation of the elastic constant versus pressure. To gain further information about this, we also have investigated the other elastic parameters (i.e., Zener anisotropy factor, Poisson's ratio, Young's modulus, and isotropic shear modulus). The electronic band structure, total and partial density of states, phonon dispersion curves, and one-phonon density of states of B2 and B32 phases are also presented with results. Key words: intermetallics, structural phase transition, elastic properties, electronic structure, vibrational properties. Nous utilisons une methode fondamentale de calcul basee sur la theorie de la fonctionnelle de densite (TFD/DFT), afin de determiner les proprietes structurelles, elastiques, electroniques et vibrationnelles de LiAl, dans l'approximation du gradient generalise (AGG/GGA) et utilisant le logiciel de simulation ab initio de Vienne (LSAV/VASP). Les resultats indiquent que LiAl est stable dans la structure B32 de type NaTl aux pressions ambiantes, ce qui est en bon accord avec les resultats experimentaux. Il y a une transition de phase structurelle du type NaTl (B32) vers le type CsCl (B2) autour de 22.2 GPa de pression. Nous analysons les effets de la pression sur les proprietes elastiques et le calcul des proprietes elastiques indique que l'instabilite elastique pourrait expliquer que la force entrainant la transition de phase est due a une variation de la dependance de la constante elastique sur la pression. Afin de parfaire l'information sur ce probleme, nous etudions les autres parametres elastiques, a savoir le facteur d'anisotropie de Zener, le rapport de Poisson, le module de Young et le module de cisaillement isotrope. Nous presentons egalement nos resultats pour la structure de bande, les densites d'etats partielles et totale, les courbes de dispersion de phonon et les densites d'etats a un phonon dans les phases B2 et B32. [Traduit par la Redaction] Mots-cles: intermetallique, transition de phase structurelle, proprietes elastiques, structure electronique, proprietes vibrationnelles., 1. Introduction Binary Li-Al alloys have received much attention from both materials science and condensed matter physics due to their outstanding properties [1]. The I-III intermetallic compounds of lithium and [...]

On the basis of first-principles calculations, we investigate the absorption of fluorine and chlorine on ferromagnetic monolayer CrN focusing on the mechanism of spin reorientation. We use density functional theory in combination with the spin Hamiltonian approach to study the electronic and magnetic properties of monolayer CrN upon single-side adsorption of F and Cl atoms. While the electronic structure of ferromagnetic CrN remains half-metallic after functionalization, its preferred axis of magnetization is rotated toward the in-plane direction due to the orbital moment suppression. The half-coverage of CrN is found to be thermodynamically stable and ferromagnetically ordered at room temperature. Our findings demonstrate the possibility of altering the magnetic properties of a two-dimensional magnet after the adsorption of F and Cl, which opens a route to the detection of these gases using magnetic or optical measurements. [ABSTRACT FROM AUTHOR]

Two-dimensional materials are leading the way in nanodevice applications thanks to their various advantages. Although two-dimensional materials show promise for many applications, they have certain limitations. In the last decade, the increasing demand for the applications of novel two-dimensional materials has accelerated heterostructure studies in this field. Hence, restoring the combination of two-dimensional heterostructured materials has been reported. In this paper, we show that the effect of the external electric field and biaxial strain on the silicene/Ga2SeS heterostructure has a critical impact on the tuning of the Schottky barrier height. The findings such as the variation of the electronic band gap, interlayer charge transfer, total dipole moment, and n-type/p-type Schottky barrier transitions of the silicene/Ga2SeS heterostructure under external effects imply that the device performance can be adjusted with Janus 2D materials. [ABSTRACT FROM AUTHOR]

Motivated by the increasing number of studies on optoelectronic applications of van der Waals (vdW) heterostructures, we have investigated the electronic and optical properties of monolayer gallium nitride (MGaN) and boron phosphide (MBP) heterobilayers by using first-principle calculations based on density functional theory. We have ensured the dynamical stability of the structures by considering their binding energies and phonon spectra. We show that the magnitude and status (direct or indirect) of the band gap are strongly dependent on the stacking pattern of the heterobilayers. Furthermore, we have investigated the band splittings in the presence of an external electric field which show the effect of the field on the band alignment of the structure. We have also shown the band gap, charge redistributions and work function of the structures are highly dependent on the magnitude and direction of the electric field such that its magnitude yields indirect to direct band gap transitions around ☋E⊥☋∼ 0.7 V Å−1 at the Γ point and the order of the band gap is varied according to the direction of the electric field. Moreover, we examine optical properties of MGaN/MBP heterobilayers as part of DFT calculations. The band gap and work function being tunable with changes in the external field together with the prominent absorption over the UV range make the MGaN/MBP heterobilayer a feasible candidate for optoelectronic applications. [ABSTRACT FROM AUTHOR]

Following its synthesis, borophene has drawn noticeable attention due to its remarkable intrinsic properties. Understanding and modifying these properties are crucial for implementation of borophene in high-technological applications. In this study, we employed ab initio techniques to examine the variation of the optoelectronic properties of buckled borophene by strain and surface functionalization. We find that the optical response can be tuned by applying compressive/tensile strain and covering the surface with hydrogen and fluorine atoms. It is shown that the variations in optical properties can be correlated with structural deformations and modifications in the electronic band structure. Revealing the tunability of the optical response of borophene can pave the way for its potential uses in various optoelectronic devices. [ABSTRACT FROM AUTHOR]

We investigate the electronic and optical properties of monolayer and stacking dependent bilayer blue phosphorus in the framework of density functional theory (DFT) and tight-binding approximations. We extract the hopping parameters of TB Hamiltonian for monolayer and bilayer blue phosphorus by using the DFT results. The variation of energy band gap with applied external electric field for two different stacks of bilayer blue phosphorus are also shown. We examine the linear response of the systems due to the external electromagnetic radiation in terms of the dielectric functions in the DFT theory. The relatively large electronic band gap and possibility of exfoliation form bulk structure due to weak interlayer coupling, make blue phosphorus an appropriate candidate for future electronic devices. [ABSTRACT FROM AUTHOR]

Using the first-principles density functional calculations, the structural, electronic and magnetic properties of the Fe 2 XAl (X=Cr, Mn, Ni) compounds in both the Hg 2 CuTi and Cu 2 MnAl-type structures were studied by the full-potential linearized augmented plane waves (FP-LAPW) method. The exchange and correlation potential is treated by the generalized-gradient approximation (GGA) where the results show that the Cu 2 MnAl-type structure is energetically more stable than the Hg 2 CuTi-type structure for the Fe 2 CrAl and Fe 2 MnAl compounds at the equilibrium volume. The full Heusler compounds Fe 2 XAl (X=Cr, Mn) are half-metallic in the Cu 2 MnAl-type structure. Fe 2 NiAl has a metallic character in both CuHg 2 Ti and AlCu 2 Mn-type structures. The total magnetic moments of the Fe 2 CrAl and Fe 2 MnAl compounds are 1.0 and 2.0 μ B , respectively, which are in agreement with the Slater–Pauling rule M tot =Z tot − 24. [ABSTRACT FROM AUTHOR]

We investigate the effect of charge carrier interaction with surface optical phonons on the band properties of monolayer black phosphorus induced by polar substrates. We develop an analytical method based on the Lee-Low-Pines theory to calculate the spectrum of Fröhlich type continuum Hamiltonian in the long-wavelength limit. We examine the modification of a band gap and renormalization of effective masses due to the substrate-related polaronic effect. Our results show that an energy gap in supported monolayer black phosphorus is enlarged depending on a particular substrate and the interlayer distance z. Among the substrate considered, the largest gap broadening at z = 2.5Å is observed for the Al2O3 substrate, which is found to be ~50 meV. Carrier-phonon coupling also renormalizes the effective masses which is more pronounced along the zigzag direction. Anisotropy of the effective masses becomes stronger by the influence of the polaronic effect corresponding to direction-dependent carrier-phonon coupling. We conclude that substrate phonons have a non-negligible effect on the static band properties of monolayer black phosphorus, which may be further exploited in its experimental and theoretical studies. [ABSTRACT FROM AUTHOR]

In this article we study the effect of applied strain on the electronic and mechanical properties of stanene, the Tin counterpart of graphene. Due to the relatively large intrinsic spin–orbit coupling we used the fully-relativistic pseudo-potentials to consider the effect of spin–orbit in the density functional calculations. The spin–orbit interaction opens a 70 meV energy gap in the K point but by applying strain the energy gap in the band structure is closed. The density functional theory and simple molecular mechanic models are used to estimate the Young’s modulus of stanene. According to our calculations we estimate the in-plane stiffness of stanene Y s = 40 N/m. By matching DFT and molecular mechanic results of stanene, we investigate the size and chirality effects on the in-plane stiffness of stanene nano ribbons. [ABSTRACT FROM AUTHOR]