Search

Using electronic structure calculations based on density functional theory, we predict and study the structural, mechanical, electronic, magnetic and transport properties of a new full Heusler chalcogenide, namely, Fe$_2$CrTe, both in bulk and heterostructure form. The system shows a ferromagnetic and half-metallic(HM) like behavior, with a very high (about 95%) spin polarization at the Fermi level, in its cubic phase. Interestingly, under tetragonal distortion, a clear minimum (with almost the same energy as the cubic phase) has also been found, at a c/a value of 1.26, which, however, shows a ferrimagnetic and fully metallic nature. The compound has been found to be dynamically stable in both the phases against the lattice vibration. The elastic properties indicate that the compound is mechanically stable in both the phases, following the stability criteria of the cubic and tetragonal phases. The elastic parameters unveil the mechanically anisotropic and ductile nature of the alloy system. Due to the HM-like behavior of the cubic phase and keeping in mind the practical aspects, we probe the effect of strain as well as substrate on various physical properties of this alloy. Transmission profile of the Fe$_2$CrTe/MgO/Fe$_2$CrTe heterojunction has been calculated to probe it as a magnetic tunneling junction (MTJ) material in both the cubic and tetragonal phases. Considerably large tunneling magnetoresistance ratio (TMR) of 1000% is observed for the tetragonal phase, which is found to be one order of magnitude larger than that of the cubic phase.

In this work, using density functional theory based electronic structure calculations, we carry out a comparative study of geometric, mechanical, electronic, magnetic, and thermoelectric properties of Co

The health insurance industry is facing many challenges such as privacy, increasing competition, rising costs, and an aging population. Artificial intelligence (AI) is increasingly being used to do risk assessments, determine premiums, prevent fraud, accelerate claims, prevent illnesses, and improve customer experience. Although AI does confer significant benefits to the health insurance industry, there are significant risks and challenges that need to be overcome that can slow down the rate of adoption or, in some cases, prevent the adoption of AI-based solutions.

Using first-principles calculations based on density functional theory along with the semi-classical transport theory, we study thermoelectric properties of Co2XGa (X = Mn, Mo, Pt) alloys. We plot the Seebeck coefficient and conductivity as a function of temperature and chemical potential, for the cubic austenite and tetragonal martensite (whenever available) phases. We also calculate the density of states. Further, we study the trend of Seebeck coefficients by analyzing the conductivity and compare the data across the materials and also for different phases.

Using first-principles calculations based on density functional theory, we have studied the X-ray absorption spectra (XAS) and X-ray Magnetic Circular Dichroism (XMCD) spectra of Co 2 PtGa and Mn 2 PtGa alloys. Using relativistic calculations, we have estimated and analyzed the contribution of the orbital and spin moments to the total magnetic moment for the transition metal atoms, Pt, Co and Mn. It has been observed that while the ratio of orbital and spin magnetic moments of Pt atom in Co 2 PtGa in cubic phase is substantial, this is an order of magnitude lower in Mn 2 PtGa. On the other hand, this difference reduces drastically in case of the martensite phase. This signifies the crucial role of the neighborhood in determining the magnetic properties of these materials. Further, the XAS and XMCD spectra at the L 2 , 3 edges of different constituent atoms in various materials have been analyzed. The results (peaks and shoulders present in these XAS and XMCD spectra) have been corroborated with the atom-projected unoccupied density of states of the respective materials.

A bandgap bowing parameter of 0.4 ± 0.2 eV for β-(AlxGa1−x)2O3 alloys, with Al compositions (x) up to 0.35, has been determined from the bandgap obtained from low temperature optical reflectivity, which suppresses the effect of electron–phonon interaction on the bandgap. A length scale of inhomogeneity of 0.21 ± 0.03 times of the electron–hole mean free path length has been estimated for β-(AlxGa1−x)2O3 alloys. The unit cell of β-(AlxGa1−x)2O3 alloys compresses, and the lattice parameters vary linearly with Al substitution. Our results provide insight into bandgap engineering and alloy disorder for β-(AlxGa1−x)2O3 alloys, which are an important material system for applications in deep ultraviolet opto-electronic devices.

Using Van der Waals dispersion corrected density functional theory, we study the adsorption of three environmentally important gases, namely, H2, CO and NO on the pristine Aluminene as well as transition metal (TM) atom substituted Aluminene surface. Interestingly, we observe enhanced adsorption of all the gases for the TM-substituted Aluminene, when compared to the pristine case. It has been found that the Kubas interaction plays an important role in stabilizing the H2 adsorption on TM-substituted systems. However, CO and NO molecular adsorption on TM-substituted Aluminene surfaces occur from the bonding of molecules to TM through the frontier orbitals of molecules, mainly, 2 π orbitals. Moreover, the reactivity trend of TM-substituted Aluminene surfaces for molecular adsorption of CO and NO gas molecules has been discussed on the basis of position of TM d-band centre. Charge analyses reveal that all the three molecules act as charge acceptors. We observe significant adsorbate-induced variations in the relative electrical conductivity values. From the results of recovery time, it is expected that the adsorption of H2 and CO gases on pristine Aluminene and H2 gas on TM functionalized Aluminene surfaces may show promises for usage as reusable gas sensor as well as gas storage with subsequent facile release.

In this work, using density functional theory based electronic structure calculations, we carry out a comparative study of geometric, mechanical, electronic, magnetic, and thermoelectric properties of Co x TaZ alloys, where Z = Si, Ge and Sn and x = 1 and 2. In the present study, a systematic approach has been taken to perform calculations to probe the possibility of existence of a tetragonal (martensite) phase in these alloys and also to perform a comparative study of various physical properties of the six systems, mentioned above, in the cubic and possible tetragonal phases. From our calculations, a tetragonal phase has been found to be stable up to about 400 K in case of Co2TaSi and Co2TaGe alloys, and up to about 115 K for Co2TaSn, indicating the presence of room temperature cubic phase in the latter alloy unlike the former two. Further, the results based on the energetics and electronic structure have been found to corroborate well with the elastic properties. All the above-mentioned full Heusler alloys (FHAs) show magnetic behavior with metallicity in both the phases. However, their half Heusler counterparts exhibit non-magnetic semi-conducting behavior in the cubic phase. We calculate and compare the thermoelectric properties, in detail, of all the materials in the cubic and possible tetragonal phases. In the cubic phase, the half Heusler alloys exhibit improved thermoelectric properties compared to the respective FHAs. Furthermore, it is observed that the FHAs exhibit higher (by about an order of magnitude) values of Seebeck coefficients in their cubic phases, compared to those in the tetragonal phases (which are of the order of only a few micro-volts/Kelvin). The observed behaviors of the transport properties of the probed materials have been analyzed using the topology of the Fermi surface.

Searching for new Heusler alloys with novel electronic and magnetic properties is a recent topic of interest to researchers. Using density functional theory based calculations, we study the effect of the replacement of Ga by Al at the A-site of A 2 BC -type alloy, Ga2MnNi. By analyzing the magnetic properties of the Ga 2 - x Al x MnNi system (with values of x between 0 and 2), we find that in Al2MnNi alloy, the Mn atom possesses a substantially lower value of moment compared to Ga2MnNi. To understand this unusual result, atom-derived spin-polarized densities of states (DOS) for the Ga 2 - x Al x MnNi system have been calculated. Analysis of Bader charge and difference charge density distribution has been found to corroborate with the DOS results. Further, we find that Al2MnNi alloy has a relatively large DOS, rather close to and below the Fermi level. Hence, electronic properties of a system with partial substitution of Ni by Co at the C-site of Al2MnNi have been probed. Combined results of calculations of Bloch spectral functions and density of states of this material suggest a large DOS almost at the Fermi level.