Флуктуации электронной плотности и фазовый переход в α-титане

It is shown that the topological features of the electronic structure of α-titanium lead to the appearance of temperature-induced fluctuations of the electron density, which disappear near the temperature of the phase transition from the hcp (α-phase) to the bcc (β-phase). The experimen-tally observed linear temperature increase in the magnetic susceptibility in the beta-phase and its jump during the transition to the β-phase are described. The considered fluctuation pattern de-scribes a sharp decrease in the electron entropy and softening of the longitudinal phonon modes associated with the electron-ion interaction. It is shown that the temperature of the phase transition in α-titanium depends on the position of the Fermi level, which can be changed by introducing impurities.

Changes in the phonon density of states of Fe induced by external strain

Nuclear inelastic scattering of synchrotron radiation is used to study the changes induced by external tensile strain on the phonon density of states (pDOS) of polycrystalline Fe samples. The data are interpreted with the help of dedicated atomistic simulations. The longitudinal phonon peak at around 37 meV and also the second transverse peak at 27 meV are decreased under strain. This is caused by the production of defects under strain. Also the thermodynamic properties of the pDOS demonstrate a weakening of the force constants and of the mean phonon energy under strain. Remaining differences between experiment and simulation are discussed.

Growth mechanism of 3D graphene-carbon nanotube hybrid structure

In this paper, a novel molecular dynamic model is presented to describe the growth mechanism of three-dimensional (3D) graphene-carbon nanotube (G-CNT) hybrid structure synthesized by catalytic chemical vapor deposition. For this purpose, first, the physisorption of a carbon atom on a graphene sheet (GS) is studied. Then the model is formulated by using kinetic theory and the longitudinal phonon oscillation of adsorbed carbon atoms on GS. Results show that the CNT grows on GS up to 0.3 mm. Also, there is an optimum temperature for growth of the 3D G-CNT hybrid structure, which can be calculated by the presented model. Finally, it is shown that increase of partial pressure leads to increase of length of growing CNT on GS.