2D as protective film – 2D as magnetic layer
IT4Innovations, VSB-TU Ostrava, Ostrava, Czech Republic
In the first part the presentation of the possible candidates for the protective layers for rechargeable batteries. These are often based on lithium (sodium) metal anodes that have been attracting increasing attention due to their high capacity and energy density, but exhibit drawbacks, such as low Coulombic efficiency and dendrites growth. Layered materials have been used experimentally as protective films (PFs) to address these issues. Here we use first-principles calculations to determine the properties and feasibility of various 2D layered PFs, including the defect pattern, crystalline structure, bond length,
and metal proximity effect, Li+ (Na+) ion diffusion, and mechanical stability. It is found that the introduction of defects, the increase in bond length, and the proximity effect by metal can accelerate the transfer of Li+ (Na+) ion and improve the ionic conductivity, but all of them make negative influences on the stiffness of materials. against the suppression of dendrite growth and weaken both critical strains and critical stress. The results provide new insight into the interaction mechanism between Li+ (Na+) ions and PF materials at the atomic level and shed light onto exploring a variety of layered PF materials in metal anode battery systems .
The second part is devoted to magnetism in 2D. For the spintronic applications like large data storages (high capacity HDD) the industry searches for ferromagnetic insulators at nanoscale size. Recently the discovery of Bi2 O2 Se/Te phases that exist as 2D material and still are semiconducting attract attention. Here we investigate Bi2-n Xn O2 Se by transitional metal doping to introduce a magnetic spin order. We explore the electronic and magnetic properties of various ferromagnetic (e.g. Fe) or antiferromagnetic (e.g. Mn) transitional metals doped Bi2 O2 Se phases within the framework of density functional theory based electronic structure calculations. We start with the magnetic order of the bulk phase in which the magnetic atoms form interlayer coupling that vary with the type and concentration of doped atoms and go towards the nanoscale dimension, i.e. 2D materials. As a result of the competitions of magnetic interactions the magnetic anisotropy energy is a crucial quantity. In combinations with Monte Carlo simulations we are able to solve the exchange interaction constants for the Heisenberg model and therefore evaluate the Curie temperature to see if these types of materials are suitable to become novel dilute magnetic semiconductors for spintronic applications at room and above temperatures .
 X. Liu et al., Phys Rev. B 100, 054438 (2019).
host: Martin Gmitra