M. Lakhal

Hydrogen storage of Mg1?xMxH2 (M = Ti, V, Fe) studied using first-principles calculations

In this work, the hydrogen storage properties of the Mg-based hydrides, i.e., Mg1−x Mx H2 (M = Ti, V, Fe, 0 ≤ x ≤ 0.1), are studied using the Korringa—Kohn—Rostoker (KKR) calculation with the coherent potential approximation (CPA). In particular, the nature and concentrations of the alloying elements and their effects are studied. Moreover, the materials stability and hydrogen storage thermodynamic properties are discussed. In particular, we find that the stability and the temperature of desorption decrease without significantly affecting the storage capacities.

First principle calculations for improving desorption temperature in Mg16H32 doped with Ca, Sr and Ba elements

Using ab initio calculations, we predict the improvement of the desorption temperature and the hydrogen storage properties of doped Mg-based hydrides such as, Mg15AMH32 (AM = Ca, Sr and Ba) as a super cell 2 × 2 × 2 of MgH2. In particular, the electronic structure has been obtained numerically using the all-electron full-potential local-orbital minimum-basis scheme FPLO9·00-34. Then, we discuss the formation energy calculations in terms of the material stabilities and the hydrogen storage thermodynamic properties improvements. Among others, we find that the stability and the temperature of desorption decrease without reducing significantly the high storage capacity of hydrogen. Moreover, it has been observed that such a doping procedure does not affect the electronic behavior as seen in MgH2, including the insulator state in contrast with the transition metal hydrides, which modify the electronic structure of pure MgH2.

Interdistance Effects on Flat and Buckled Silicene Like-bilayers

Using ab intio numerical calculations based on the all-electron full-potential local-orbital minimum-basis scheme FPLO9.00-34, we discuss the interdistance effect on the energy gap of two parallel layers of the silicone systems. The like- bilayer systems we dealt with here are relying on a dynamic monolayer of silicene located at distance d along the normal direction z forming with a static one a (AA) stacking arrangement. In particular, we investigate the effect of the dynamic layer by varying the distance d starting from a distance around the bond length of Van der Waals. More precisely, we consider the flat and two buckled geometries in (AA) arrangements. The flat geometry is associated with the usual (AA) configuration appearing in the pure graphene material. For buckled geometry, we can distinguish two configurations. The first one corresponds to the usual buckled configuration that keeps the same vertical distance between the two layers atoms while the remaining one is obtained by reversing one silicene layer. We show that the band gap can be opened by simply varying the distance, starting around a Van der Waals distance, between two parallel silicene for flat and buckled geometries due to an electronic transition of electrons living in pz orbital states. Furthermore, we study the stability between the buckled and the flat configuration in the mono and bilayer system.

Compression effect on electronic properties and hydrogen desroption of LiBH4: First principal study

The structure, stability, dehydrogenation properties of LiBH4 under compression were considered by using first principles calculations based on the density functional theory (DFT). The result indicate that compression strain is expected to cause a structural deformation of LiBH4 crystal, because of the contribution of compression strain energy. We found that also the hydrogen desorption enthalpy decreased when compression strain applied on LiBH4 structure. Furthermore, the calculation of electronic structure indicates that compressions strain influence on total density of state. These results are beneficial to improve the thermodynamic properties.