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[en] The kinetics of the semi-infinite Ising model in the presence of a time-dependent oscillating external field is studied within the framework of the mean-field approach. We use the Glauber-type stochastic dynamics to describe the evolution time of this system. We present a variety of phase in a semi-infinite cubic ferromagnet with spin-1 in two different, planes; phase diagrams contain (BF, S 1P, SP) phase, (BF, S 1F, SP) phase, completely ordered phase (BF, S 1F, SF) and completely disordered phase (BP, S 1P, SP), which strongly depend on interaction parameters. The nature first and second orders of the transitions is characterized by studying the thermal behaviors of the dynamic magnetizations. Furthermore, the system exhibits dynamical tricritical phenomenon and the reentrant behaviors. The magnetizations and phase space trajectories are given and discussed.
[en] In this work, we present a study of hydrogen atoms interacting with hydrogen, nitrogen, and oxygen molecules in the gas phase in order to determine the projectile energy loss, the stopping cross section, and energy deposition with implication in hydrogen and proton dosimetry and radiotherapy. Our calculations are performed with a density-functional tight-binding (DFTB) as well as by an ab initio electron-nuclear dynamic (END). The H atoms have a low collision energy in the range of 1–100 eV for the DFTB and 1–1000 eV for the END. We decompose the projectile energy deposition into its electronic, nuclear, rotational, and vibrational energy target contributions. We find that for low collisions energy, DFTB and END are in fair agreement when comparing the nuclear and rotational contributions. However, we find discrepancies for the vibrational and electronic energy loss between both approaches. The largest discrepancy is found in the electronic energy loss as DFTB carries the electronic dynamics in the ground state. We confirm that the electronic stopping cross section is proportional to the projectile velocity as obtained by END showing a threshold effect and that it is underestimated by codes like SRIM. Our study shows that at low collision energies a quantum-classical molecular dynamics approach as DFTB can be used to determine the energy-loss process of a projectile penetrating a material target. Finally, we compare our results to available experimental data finding good agreement when extrapolated to high collision energies. (paper)
[en] The structural and electronic properties of the monolayer and bilayer stanene structures have been studied using first-principles calculations. For the monolayer, the buckled structure is more stable than the flat one, with an opening of the band gap when spin-orbit coupling is taken into account, as mentioned in recent studies. For the bilayer, three types of stacking are considered: parallel layers, anti-parallel layers, and parallel layers where the first layer is shifted from the second one. These three configurations are named AA1, AA2, and AB, respectively. The two layers are separated by the distance d. The interactions between two layers of stanene are strong for a short distance, while the van der Waals bonding appears for a longer distance. Furthermore, stanene was fabricated experimentally on a substrate; thus, we proposed another study of electronic properties of stanene deposited on Ge(111) to reveal other behavior as a topological insulator and show the existence of the quantum spin Hall effect.