The Earth's core contains, in addition to iron, 5-10% nickel and many light elements such as C, O, Si and S, among others. For this work, we consider binary Fe-Ni alloys with 10% Ni as host material, doped with light elements as impurity atoms. The phases considered for the Fe-Ni host alloy are face-centered cubic (fcc) and body-centred cubic (bcc). At different concentrations of 2.5-50%, the impurity atoms C, O, Si and S were placed in the host Fe-Ni alloy to create ternary alloys. The resulting ternary systems are exposed to a pressure equivalent to that existing at the Earth's core. As shown by their formation energies, these alloys are stable and advantageous. The calculation of the resistivity of the impurities was performed with the help of the Kubo-Greenwood formula. Compared to fcc, in the case of bcc, electrical resistivities begin to saturate at about 30% of the atomic concentration of the impurities. Thermal conductivity was also determined from electrical resistivities calculated for varying concentrations and pressures according to Wiedemann-Franz law. In the case of compression, we observe a rise in thermal conductivity of about 1.5% of the core's internal pressure. The reported thermal conductivities support the notion of maintaining a convection-induced geodyanmo.

In search of high energy density cathode materials, the eldfellite mineral-type NaVIII(SO4)2 compound has been theoretically predicted to be a promising cathode insertion host for sodium-ion batteries. Synergizing computational and experimental investigations, the current work introduces NaVIII(SO4)2 as a novel versatile cathode for Li-ion and Na-ion batteries. Prepared by a low temperature sol-gel synthesis route, the eldfellite NaV(SO4)2 cathode exhibited an initial capacity approaching ∼79% (vs. Li+/Li) and ∼69% (vs. Na+/Na) of the theoretical capacity (1e− ≅ 101 mA h g−1) involving the V3+/V2+ redox potential centered at 2.57 V and 2.28 V, respectively. The bond valence site energy (BVSE) approach and DFT-based calculations were used to gain mechanistic insight into alkali ion migration and probe the redox center during (de)insertion of Li+/Na+ ions. Post-mortem and electrochemical titration tools revealed the occurrence of a single-phase (solid-solution) redox mechanism during reversible Li+/Na+ (de)insertion into NaVIII(SO4)2. With the multivalent vanadium redox center, eldfellite NaVIII(SO4)2 forms a new cathode insertion host for Li/Na-ion batteries with potential two-electron uptake. 

The developmental rapidity of nanotechnology poses higher risks of exposure to humans and the environment through manufactured nanomaterials. The multitude of biological interfaces, such as DNA, proteins, membranes, and cell organelles, which come in contact with nanoparticles, is influenced by colloidal and dynamic forces. Consequently, the ensued nano-bio interface depends on dynamic forces, encompasses many cellular absorption mechanisms along with various biocatalytic activities, and biocompatibility that needs to be investigated in detail. Addressing the issue, the study offers a novel green synthesis strategy for antibacterial AgNPs with higher biocompatibility and elucidates the mechanistic in vivo biocompatibility of silver nanoparticles (AgNPs) at the cellular and molecular levels. The analysis ascertained the biosynthesis of G-AgNPs with the size of 25 ± 10 nm and zeta potential of-29.2 ± 3.0 mV exhibiting LC50 of 47.2 μg mL-1 in embryonic zebrafish. It revealed the mechanism as a consequence of abnormal physiological metabolism in oxidative stress and neutral lipid metabolism due to dose-dependent interaction with proteins such as he1a, sod1, PEX protein family, and tp53 involving amino acids such as arginine, glutamine and leucine leading to improper apoptosis. The research gave a detailed insight into the role of diverse AgNPs-protein interactions with a unique combinatorial approach from first-principles density functional theory and in silico analyses, thus paving a new pathway to comprehending their intrinsic properties and usage.

The thermodynamic and physical properties of Helium (He) and Hydrogen (H) mixtures are crucial form an astrophysical perspective. Nowadays, it is well known that these two elements constitute roughly 95% of the matter in the solar system. The high-pressure equation of He state doped with H is calculated in the framework of density functional theory (DFT) for three crystallographic structures. Namely, the Body Centered Cubic (BCC), Face Centered Cubic (FCC), and hexagonal close packed (HCP) structures have been studied. The equations of state (EOS) are provided for the He0.90H0.10 and He0.70H0.30 mixtures and the energy of the same mixtures are calculated with the earlier structures. The band structure for pressures of 0, 75 and 150 GPa were estimated by our calculations for the presumed crystal structures in the case of pure He and He0.70H0.30 mixture for comparison. The k(x) - k(y) cuts of the Bloch Spectral Functions (BSF) are presented for the pure He and He0.70H0.30 mixture for the three structures to explore the impact of doping on electronic properties. In addition, electrical resistivity calculations of the mentioned structures were carried out for mixtures with 10, 15, 20 and 30% of H. At final stage, the enthalpy (Delta H) of these latest mixtures have been deduced for the three crystal structures.

An unprecedented graphyne allotrope with square symmetry and nodal line semimetallic behavior has been proposed in the two-dimensional (2D) realm. The emergence of the Dirac loop around the high-symmetry points in the presence of both the inversion and time-reversal symmetries is a predominant feature of the electronic band structure of this system. Besides, the structural stability in terms of the dynamic, thermal, and mechanical properties has been critically established for the system. Following the exact analytical model based on the realspace renormalization group scheme and tight-binding approach, we have inferred that the family of 2D nodal line semimetals with square symmetry can be reduced to a universal four-level system in the low-energy limit. This renormalized lattice indeed explains the underlying mechanism responsible for the fascinating emergence of 2D square nodal line semimetals. Besides, the analytical form of the generic dispersion relation of these systems is well supported by our density-functional theory results. Finally, the nontrivial topological properties have been explored for the predicted system without breaking the inversion and time-reversal symmetry of the lattice. We have obtained that the edge states are protected by the nonvanishing topological index, i.e., Zak phase.

The Lithium-sulfur (Li-S) battery chemistries have so far been plagued with difficulties such as the dissolution of intermediate lithium-polysulfides (LPSs) into the electrolyte, the so-called shuttle-effect, causing the capacity loss. Using van der Waals corrected density functional theory approach, we report the outstanding anchoring effect of germanene monolayer (GeM), which can trap the LPSs sturdily without disturbing their integrity. The persistent electrical conductivity of GeM upon adsorption of LPSs demonstrates an effective strategy for the enhanced cyclic performance of Li-S batteries while avoiding the shuttling effect and preventing agglomeration at the battery electrodes. It is found that the LPSs adsorbed to GeM with a moderate assortment between -1.8. to -2.6 eV. In addition to the efficient anchoring performance, the electronic properties of GeM also improve upon the adsorption of LPSs. The diffusion barrier energies of LPSs are very small, thus ensuring their ultrafast diffusion and smooth transition during the charge/discharge process of the Li-S battery.

The body-centered cubic (bcc) to face-centered cubic (fcc) phase transition of magnesium is explained by Bain deformation using first-principles calculations. It is shown that the bcc structure transforms into the fcc structure at a pressure of 489 GPa. The electronic band structure of the bcc structure exhibits the Lifshitz transition. The projected density of states of the bcc structure displays the s–d hybridization near the Fermi energy under high pressure. This remarkable structural feature shows the unique pathway leading to a common bcc–fcc Bain deformation mechanism among alkaline-earth metals.

The low cost, high energy density, and nontoxic nature have made lithium-selenium batteries (LiSeBs) a promising option for large-scale energy storage applications. However, the issue of capacity loss during consecutive charge/discharge cycles has put a serious question mark on the commercialization of LiSeBs. In a quest to suppress the issue of capacity loss due to the dissolution of active lithium polyselenides (Li2Sen, n = 1-8) into the electrolyte, the so-called shuttle effect, we have employed first-principles density functional theory calculations to study the anchoring properties of two carbon nitrides monolayers, namely, nitrogenated holey graphene (C2N) and carbon nitride (C3N). We find that the presence of nitrogen (N) atoms, in both C2N and C3N, enable them to bind Li2Sen clusters stronger than that of graphene. We further discover that the anchoring properties of C2N (-2.03 to -3.82 eV) are stronger than that of C3N (-1.21 to -1.30 eV) due to higher concentrations of N atoms and relatively bigger pore size in the former than the later. In addition to the appropriate bindings, improved conductivities upon the adsorption Li2Sen further reinforce the promise of C2N and C3N as potential anchoring materials for LiSeBs. We believe that our computational results would pave the way toward the experimental synthesis of efficient anchoring materials based on the studied systems.

In this work we have investigated the dissociation of hydrogen rich CH4 and NH3 molecules along with CO2 on the surface of pristine and various defect induced TiS2 monolayer. The aim is to see whether the monolayer surfaces are able to produce H2 by decomposing the feedstock adsorbates and also to examine whether it can be a sorbent for CO2. We have tried to explore a monolayer surface which can simultaneously act as a catalyst to dissociate CH4, as well as to adsorb CO2 which is the only harmful by-product in steam reforming method for hydrogen production from CH4. The hydrogen generation has been predicted from the nature of gas adsorption, and the adsorption energies have been estimated to see whether it falls under chemisorption or physisorption range. Both S and Ti vacancy defects have been studied and the first-principles electronic structure calculation helps to envisage the charge redistribution of the three adsorbates on both pristine and defective TiS2 surfaces.

Economic and efficient bifunctional electrocatalysts are pivotal in realization of rechargeable (hybrid) metal-air batteries. It is ideal to employ noble-metal free bifunctional electrocatalysts that are not selective towards oxygen evolution and reduction (OER and ORR) activities. This work unveils cobalt-based tetraphosphate K2Co(PO3)(4) as an economic bifunctional electrocatalyst acting as cathode for rechargeable hybrid sodium-air batteries. Auto combustion route led to the development of homogeneous, carbon-coated, spherical K2Co(PO3)(4) nanoparticles enabling active site exposure to incoming guest molecules (O-2, OH-). This monoclinic compound exhibited superior oxygen evolution activity with low overpotential (ca. 0.32 V) surpassing the commercial RuO2 catalyst. Tetraphosphate K2Co(PO3)(4) was successfully implemented in hybrid Na-air batteries delivering reversible cycling with roundtrip efficiency over 70%. DFT study revealed this catalytic activity stem from the most active and stable surface (001) and half-metallic nature of Co in K2Co(PO3)(4). Cobalt tetraphosphates can be harnessed to design low cost electrocatalysts for hybrid sodium-air batteries.