S. Guerini

Vibrational properties of RbNd(WO4)2: high pressure Raman study, structural and phonon calculations

RbNd(WO(4))(2) was investigated by high pressure Raman spectroscopy in the 0.1-12.3 GPa pressure interval. The assignment of modes was made based on lattice dynamics calculations and the results of these calculations helped us to also discuss the high pressure behavior of phonon spectra in this material. Our results show that a double oxygen bridge plays a fundamental role in the vibrational properties of this system. A density functional theory (DFT) calculation of hydrostatic pressure effects on RbNd(WO(4))(2) was performed in order to understand the effect of internal bond changes on the vibrational properties of RbNd(WO(4))(2). No pressure induced structural phase transition was observed in the Raman study at room temperature, and the DFT calculation (T = 0 K) is consistent with this result. The anomalous softening of the bridge stretching mode at 770 cm(-1) was attributed to the decrease of W-O1-W bond angle with increasing pressure.

B and N-doped double walled carbon nanotube: a theoretical study

The structural and electronic properties of boron and nitrogen atom substitutional doping in (8,0)@(13,0) (semiconductor@semiconductor) and (6,0)@(13,0) (metallic@semiconductor) double walled carbon nanotubes, were obtained by using the first-principle calculations based on the density functional theory. In this framework, the electronic density plays a central role and it was obtained from a self-consistent field form. When boron or nitrogen substitutes a carbon atom the structure remains practically the same with negligible deformation observed around defects in all configurations considered. The electronic band structure results indicate that the boron doped systems behave as a p-type impurity, however, the nitrogen doped systems behave as an n-type impurity. In all the systems investigated here, we found that, in the cases of semiconductor@semiconductor tubes, they were the easiest to incorporate a B atom in the outer-wall and an N atom in the inner-wall of the nanotube.

Theoretical study of NO3− interacting with carbon nanotube

This paper deals with quantum mechanical interaction of no3− with (5,5) and (8,0) swcnts. To perform this we have made an ab initio calculation based on the density functional theory. In these framework the electronic density plays a central role and it was obtained of a self-consistent field form. It was observed through binding energy that NO3− molecule interacts with each nanotube in a physisorption regime. We propose these swcnts as a potential filter device due to reasonable interaction with NO3− molecule. Besides this type of filter could be reusable, therefore after the filtering, the swcnts could be separated from NO3− molecule.

Electronic properties of FeCl 3 and CrO 3 interacting with GaN nanotubes from density functional calculations

AbstractThe structural and electronic properties of FeCl3 and CrO3 interacting with (10,0) GaNNT were obtained using first principles calculations based on the density functional theory. The results show that for the CrO3 interacting with the GaNNT, the structure was locally deformed. However, in case of FeCl3 adsorbed with the GaNNT, the structure remained practically the same with the negligible deformation observed on tube surface. The projected density of states for the pristine GaNNT was modified with adsorption of FeCl3 molecule by the appearance of three strongly localized states in gap region. In case of GaNNT plus CrO3 molecule, one strongly localized level appeared in energy gap region with high contributions of molecule atoms. The analysis of the binding energy shows that the CrO3 interacting with the GaNNT is more favorable and the process occurs through chemisorption regime in both systems. Graphical AbstractProjected density of states of pristine GaNNT and FeCl3 interacting with GaNNT.

Electronic properties modifications of single-wall boron nitride with lithium atom intercalation

In this work we use the ab initio calculations to study the intercalation of lithium (Li) atoms in the channels of the single-wall boron nitride nanotube (BNNT) bundles. The relaxed structure as well as the electronic band structure were obtained. Results reveals that Li insertion modifies the band structure by shifting the Fermi energy to conduction band. The Li atoms act as electron donors and this modifies the electronic properties of the BNNT bundles due the intercalation. The electronic properties changes induced in the effects are dependent on Li atom numbers per nanotube.