Gandi, Appala Naidu

Li-ion batteries are key electric energy storage devices due to high energy density and long cycling lifetime, being widely used in portable electronic devices and large scale systems. In spite of stable cycling performance, the graphite electrode suffers from a low capacity. It is demonstrated in this context that oxygen doping makes MgCl2 electrochemically active. Importantly, the doped structure delivers a high capacity of 941 mAh g−1 for the bulk and 1098 mAh g−1 for the monolayer. The diffusion barrier is calculated to be lower than 0.6 eV. Hexagons and octahedrons composed of Li and Cl atoms are gradually formed with increasing Li coverage, breaking the Mg–Cl bonds.

Metal-ion batteries are widely used energy storage devices. Commercial cathode materials show high voltages but low capacities, limiting energy densities. Although phosphorene has been prepared and delivers a high capacity, the low voltage is problematic for cathode. The structural, electronic, and electrochemical properties of F-decorated phosphorene for metal-ion batteries are investigated using first-principles calculations. The F atoms are converted during lithiation/sodiation/potassiation. Importantly, F-decorated phosphorene delivers a capacity of 536 mAh/g and voltages of 3.46, 3.09, and 2.95 V for lithiation, sodiation, and potassiation, respectively, which leads to high energy densities of 1856, 1657, and 1582 mWh/g. Graphene coating improves stability of F-decorated phosphorene.

Recently, researchers have focused on developing more stable, Pb-free perovskites with improved processing efficiency and notable light harvesting ability. In this regard, Sn-based (Sn-b) perovskites have gained considerable interest in developing eco-friendly perovskite solar cells (PSCs). However, the oxidation of Sn2+ to Sn4+ deteriorates the performance of Sn-b PSCs. Nevertheless, this issue could be mitigated by doping alkaline earth (AE) metal. Herein, we have studied the significance of AE doping on CsSnX3 (X = Br, I) perovskites using density functional theory based calculations. The structural, electronic, and optical properties of CsAE y Sn1−y X3 (y = 0, 0.25; AE = Be, Mg, Ca, Sr) compounds were systematically investigated to explore potential candidate materials for photovoltaic applications. Formation energy calculations suggested that the synthesis of other AE-doped compounds is energetically favorable except for the Be-doped compounds. The band gaps of the materials were calculated to be in the range of 0.12-1.02 eV using the generalized gradient approximation. Furthermore, the AE doping considerably lowers the exciton binding energy while remarkably enhancing the optical absorption of CsSnX3, which is beneficial for solar cells. However, in the case of Be and Mg doping, an indirect band gap is predicted. Our theoretical findings demonstrate the potential of executing AE-doped perovskites as absorber material in PSCs, which could deliver better performance than pristine CsSnX3 PSCs.

Aqueous Zn batteries, which use metallic Zn as anodes, have gained significant attention due to their affordability and high safety standards. However, these Zn anodes are plagued by issues such as Zn dendritic growth and side reactions, including corrosion and hydrogen evolution. One straightforward yet effective approach to mitigate these issues is to apply protective coatings to the Zn anodes to enhance their reversibility. It is generally believed that these protective layers should have a high affinity for Zn. Contrarily, this study proposes that non-conductive coatings should form a strong binding with H+ ions while maintaining a weaker interaction with Zn2+ ions, thereby ensuring a higher selectivity for H+ over Zn2+. This concept is illustrated using zirconium dioxide (ZrO2), an ionic conductor that meets these criteria and effectively curbs side reactions and dendritic growth of Zn. Remarkably, Zn anodes coated with ZrO2 layer demonstrate a lifespan exceeding 6000 h at 1 mA cm−2 and 1 mAh cm−2, significantly outperforming uncoated ones, which last <200 h. This discovery introduces a novel design principle for insulating surface coatings, potentially applicable not only for Zn but also for other metal anodes.

In this study, we simulated the solidification behavior, microsegregation, and heat treatment in Fe–xMn–7.5Al–5Cr–1.0C lightweight steels using the CALculation of PHAse Diagrams method. The solidification paths and microsegregation of these steels were calculated with the Scheil-Gulliver model and equilibrium calculator in the Thermo-Calc® software. At the same time, thermodynamic calculations predicted heat-treatment temperatures for different steels. The transformation path of the Fe–xMn–7.5Al–5Cr–1.0C (x = 18 and 20 wt.%) lightweight steels is as following: liquid → liquid + δ-ferrite → δ-ferrite + γ-austenite → γ-austenite → γ-austenite + M7C3, according to equilibrium and Scheil’s calculations. In case of 25 wt.% Mn steel, the two-phase region of δ-ferrite and γ-austenite is absent in the transition path. The segregation behaviour of solute elements in the liquid, ferrite, and austenite phases were predicted using the Scheil model. The heat treatment temperature for single-phase formation is expected to be between 900 °C and 1030 °C.

Mg–Sn–Gd alloys can be considered prospective contenders for creep applications owing to the formation of thermally stable phases. In the present investigation, the solidification behaviour of Mg–Sn–Gd alloys was analysed from cooling curves obtained from thermal analysis within the temperature range of 700–300 °C. The phase evolution as a function of Sn and Gd content was studied by varying the ratio of Sn to Gd (Sn/Gd) at three levels (0.5, 1, and 2) up to a maximum concentration of 3 wt% Sn and Gd, respectively. The phases in the as-cast microstructure were compared with the phases predicted by a commercially available thermodynamic database, and a deviation was observed. The results indicated that the addition of Sn and Gd promoted the formation of a ternary MgSnGd phase. Moreover, the presence of the MgSnGd phase in the microstructure led to significant grain refinement, and its role as a potential grain refiner has been recognized.

Organic–inorganic hybrid materials are of significant interest owing to their diverse applications ranging from photovoltaics and electronics to catalysis. Control over the organic and inorganic components offers flexibility through tuning their chemical and physical properties. Herein, it is reported that a new organic–inorganic hybrid, [Mn(C 2 H 6 OS) 6 ]I 4 , with linear tetraiodide anions exhibit an ultralow thermal conductivity of 0.15 ± 0.01 W m −1 K −1 at room temperature, which is among the lowest values reported for organic–inorganic hybrid materials. Interestingly, the hybrid compound has a unique 0D structure, which extends into 3D supramolecular frameworks through nonclassical hydrogen bonding. Phonon band structure calculations reveal that low group velocities and localization of vibrational energy underlie the observed ultralow thermal conductivity, which could serve as a general principle to design novel thermal management materials.

All inorganic CsPbI3 perovskites have emerged as a potential candidate for next-generation photovoltaics (PVs) and optoelectronics. In this article, the influence of hydrostatic pressure on the structural, electronic, and optical properties of CsPbI3 perovskites was investigated using first-principles calculations within the framework of density functional theory (DFT). At 0 GPa, the orthorhombic δ-phase was found to be the most stable phase, while the α-phase is the most unstable phase. Within the applied pressure range of 0-2 GPa, δ-CsPbI3 was found to be thermodynamically stable; however, β- and γ-CsPbI3 exhibited thermodynamic stability up to 0.8 and 1.6 GPa. On the contrary, the cubic phase was thermodynamically stable only at 0 GPa. Phonon dispersion relations revealed that α- and β-phases are dynamically unstable, whereas γ-CsPbI3 is dynamically stable within the applied pressure range. Electronic structure results revealed that the band gap of α- and β-CsPbI3 decreases with increasing pressure, whereas γ-CsPbI3 showed a non-monotonic band gap variation as a function of pressure. In addition, all the three phases exhibited strong optical absorption in the visible region, and the absorption peak was radically red-shifted with applied pressure. These findings would be beneficial for experimental study and imply that pressure plays an important role in determining the properties of the CsPbI3 perovskite.

The influence of surfaces and interfaces on the Raman spectra of boron carbide crystal is studied employing first-principles calculations. Surfaces based on {10-11} planes and {01-12} planes are considered. The average energy of the {01-12} surfaces (3.26 J/m2) agrees with the experimentally reported surface energy (3.21 J/m2). Two peaks are observed at ∼270 cm−1 and ∼320 cm−1 in the calculated Raman spectra for the supercells built on the {01-12} planes. This result suggests that the experimentally observed Raman peaks at these two frequencies are more likely to originate from the surface. Two Raman peaks experimentally observed at ∼1330 cm−1 and ∼1520 cm−1 in the amorphized samples were reproduced in the Raman spectra calculated for the supercells built on the {10-11} planes. Therefore, the experimentally observed new Raman activity at ∼1330 cm−1 and ∼1520 cm−1 is more likely to originate from the interface between the amorphous and crystalline regions.

New 2D layered materials WX2N4(X≐Si, Ge)1 are suitable for thermoelectric applications for a pretty good value of the figure of merit (ZT). Here, the thermoelectric properties of the 2D monolayer of WX2N4(X≐Si, Ge) using Density Functional Theory (DFT) is investigated combined with Boltzmann Transport Equation (BTE) along with spin-orbit coupling (SOC). An excellent thermoelectric (Formula presented.) of 0.91 (0.92 with SOC) is obtained at 900 K for p-type WGe2N4, and a (Formula presented.) of 0.81 (0.86 with SOC) is observed for n-type at the same temperature. Furthermore, the WGe2N4 showed a (Formula presented.) of more than 0.7 (0.79 with SOC) at room temperature for p-type. On the other hand, the WSi2N4 showed a comparatively lower (Formula presented.) at room temperature. However, the (Formula presented.) value increases significantly at higher temperatures, reaching 0.72 (0.79 with SOC) and 0.71 (0.62 with SOC) for p and n-type at 900 K, respectively. The electronic band structure is examined and discovered that WSi2N4 and WGe2N4 possess indirect bandgaps (BG) of 2.68 eV (2.57 eV with SOC) and 1.53 eV (1.46 eV with SOC), respectively, according to Heyd-Scuseria-Ernzerhof (HSE) approximation. These materials may also be useful in UV and visible range optoelectronic devices because of their strong absorption in the respective regions.