AbstractGround state geometry, energetics, and bonding of pure Lin ( n = 2 – 9 ) and impureLinSn ( n = 1 – 8 ) small clusters are investigated using the density functional theory. Introducing a single Sn impurity significantly changes the geometry of the host clusters for n > 5. Although the Sn atom is not trapped inside the cluster, it has the greatest coordination number among other atoms in the cluster. The analyses showed that the nearest neighbor bond lengths in Sn are approximately 10% shorter than those in Li. The results elucidate that the binding energy per atom in impure clusters is greater than that in pure clusters. Finally, it is shown that for and Li8 and Li4Sn clusters that each have with eight valence electrons, the greater gap in the highest occupied molecular orbital and the lowest unoccupied molecular orbital results in a more stable cluster. Manuscript profile

AbstractEffects of geometrical asymmetry on spintronic properties of Fe/ZnO/Fe magnetic tunnel junction based on zinc oxide barrier tunnel with rock-salt crystalline structure is studied. Simulations are performed using density functional theory, and substituted layers of C, Mg, Al, Mo, and Ta are used to make geometrically asymmetric structures. The results indicate that this asymmetry has a substantial influence on the properties of the spin-dependent electronic transport, conductance, and the tunneling magneto-resistance (TMR) ratio of the pristine symmetric structure. Additionally, it is shown that geometrical asymmetry results in a sharp decrease in the TMR ratio in one of these junctions and causes a negative TMR ratio in the other four asymmetric structures. Due to the large conductance of the three pristine, C and Al substituted structures in the PA configuration, these structures can be used to generate the current with pure spin for experimental purposes. Manuscript profile

AbstractUsing density functional theory, effects of Na- and Cu-substituted layers on the spin-dependent electronic transport properties of Fe/ZnO/Fe magnetic tunnel junction based on zinc oxide barrier tunnel, with rock-salt crystalline structure, have been studied. In zero-bias voltage, conductance and tunneling magneto-resistance (TMR) ratio of structures are calculated. It is showed that substituted layers in the pristine junction greatly affect conductance and TMR ratio of this junction. The results indicated that Cu-substituted layer with reducing conductance of pristine structure in the antiparallel alignment configuration, and increasing its conductance in the parallel alignment, leads to a large TMR ratio, up to 1800%. Due to the large conductance of pristine and Cu-substituted devices in the parallel alignment, these structures would be very beneficial for experimental applications that require the spin-polarized current. Manuscript profile