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The article focuses on a study which examines the potential of sodium or Na+/vacancy disordering in improving the cycling stability, kinetics and capability of Na-ion batteries (NIBs). The study involved methods including the synthesis of P2-NaNM and P2-NaNMT compounds, electrochemistry, and density functional theory (DFT) calculations. Results are provided with information on P2-NaNM and P2-NaNMT crystal structures, electrochemical performance and charge compensation mechanism.

Ab initio calculations of electronic, magnetic and optical properties of defected (beryllium (Be) doped or void induced) buckled free standing (FS) germanene have been explored. Concentrations of doping as well as vacancy (keeping a fixed low amount of Be) are increased thoroughly, in order to study the modifications of different physical properties critically. Our study reveals that, incorporation of doping and void destroy Dirac cone in band structure of germanene. Finite bandgap for the requirement of field effect transistor (FET) applications is obtained in case of semiconducting configuration with 15.62% doping concentration. Magnetism is also induced for doping of Be with high concentration only, which is supported from projected density of states (PDOS) and charge density analysis. Anisotropic effects are prominent in optical properties like dielectric functions, absorption spectra, reflectivity and its modulation and conductivity. Static real part of dielectric constant increases linearly with increase in doping concentration but decreases with increase in vacancy concentration considering parallel polarization of electro-magnetic (EM) wave. Predicted computational results of plasma frequencies are in well agreement with expected analytical data. Peak corresponding to maximum intensity of electron energy loss spectra (EELS) appears at the position of plasma frequency in case of every structure. We expect, this study may help for better understanding of next generation germanene based nano-technology. [ABSTRACT FROM AUTHOR]

The core structures and mobility of ⟨c⟩ dislocations in magnesium were predicted using both density functional theory and molecular dynamics simulations. The pure edge and screw cores are compact at 0 K. With increasing temperature up to 700 K, the edge dislocation dissociates into two ⟨c⟩/2 partials on the basal plane, but remains immobile. The screw dislocation remains compact and continuously cross-slips between the three prismatic planes. At room temperature, the screw dislocation only glides after emitting a vacancy at 420 MPa. The Peierls stress of the dislocation after vacancy emission is 50 MPa. [ABSTRACT FROM AUTHOR]

The behavior of atomic hydrogen in osmium dioxide and ruthenium dioxide is investigated through ab initio calculations using density functional theory. Interstitial hydrogen behaves as a donor in both metal oxides and only has one stable interstitial position, bonding with an O atom to form an OH O defect. The rates of diffusion parallel to the c -axis are estimated to be 3.95 × 10 − 7 exp(−0.793/ k B T ) m 2 /s and 3.64 × 10 − 7 exp(−0.659/ k B T ) m 2 /s in OsO 2 and RuO 2 , respectively. The rates of diffusion perpendicular to the c -axis are estimated to be 1.80 × 10 − 6 exp(−0.941/ k B T ) m 2 /s and 1.10 × 10 − 6 exp(−1.21/ k B T ) m 2 /s in OsO 2 and RuO 2 , respectively. Additionally, the binding energy of multiple H atoms in (O, Os, Ru) vacancies have been calculated. High binding energies of hydrogen in metal vacancies result in multiple H atoms associating with a single metal vacancy. In RuO 2 , the binding energy of multiple H atoms outweighs the formation energy of a single Ru vacancy as well as that of a Ru–O divacancy. [ABSTRACT FROM AUTHOR]