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Structural Disorder in Quasicrystals

Strzałka R., Bugański I., Śmietańska J., Wolny J.

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 1

291--294

EN

One of the challenges of modern crystallography of complex systems (complex metallic alloys, proteins, aperiodic crystals and quasicrystals) is to properly describe the disorder in these systems and discuss correctly the refinement results in terms of the structural disorder. In this paper we briefly discuss a new approach to phasons and phonons in quasicrystals and focus on the new theory of phonons in these materials. A newly derived correction factor for phonons in the form of the Bessel function is the approximated way of describing optic modes in the phonon spectra of quasicrystals. It is applied to a real decagonal quasicrystal in the Al-Cu-Rh system with 56/38 atoms per thick/thin structural unit, based on 2092 unique reflections selected from the collected diffraction data, significantly improving the refinement results. The final R-factor value is 7.24%, which is over 0.5% better result comparing to originally reported. We believe our work will open a broader discussion on the disorder in quasicrystals (and other aperiodic systems) and motivate to develop new approaches to treat the diffraction data influenced by different types of disorder in the new way.

2

The interval lattice Boltzmann method for transient heat transport

Piasecka Belkhayat A.

Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej

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2009

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Vol. 8, nr 1

155-160

EN

In this paper an application of the interval lattice Boltzmann method for solving one-dimensional problems is presented. The Boltzmann transport equation transformed in the phonon energy density equation is considered. Such approach in which the parameters appearing in the problem analyzed are treated as the constant values is widely used. Here, the model with interval value of relaxation time is analyzed. In the final part of the paper, results of numerical computations are shown.

3

Phonon-assisted tunneling through a quantum dot coupled to magnetic leads

Rudziński W

Materials Science Poland

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2008

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Vol. 26, No. 4

879--883

EN

We study theoretically spin-polarized transport in double barrier tunneling junctions based on a single level quantum dot interacting with a local phonon mode. It is shown that the electron-phonon interaction gives rise to oscillations of the tunnel magnetoresistance (TMR). In asymmetrical junctions, the polaronic transport through the junction may lead to a significant suppression of the diode-like behavior. The case of negative effective charging energy is also analyzed numerically. It is shown in particular that for a mesoscopic diode an interplay between the single -electron cotunneling and the pair tunneling processes leads to inversion of TMR.

4

First-principles calculations of vibrational and thermodynamical properties of solids

Parlinski K.

Materials Science Poland

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2005

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Vol. 23, No. 2

357--363

EN

The presented first-principle phonon calculations make use of the standard DFT program, and the direct method. The procedure requires optimization of the structure, calculation of the forces, and construction of the dynamical matrix. This method has already been applied to a large number of crystalline systems to calculate the phonon dispersion curves, phonon density of states, and thermodynamic functions, which were required for a description of phase transitions.

5

Optical properties of fluoroindate glasses doped with rare earth ions.

Gabryś-Pisarska J., Żelechower M., Pisarski W.A., Gołąb S., Bałuka M., Ryba-Romanowski W.

Optica Applicata

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2000

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Vol. 30, nr 4

517-528

EN

Multicomponent indium based fluoride glass singly doped with europium, terbium, holmium and thulium has been investigated using methods of optical spectroscopy. Owing to low energy of phonons available in the glass matrix, the luminescent levels of rare earth ions are depopulated mainly by radiative transitions and nonradiative ion-ion interaction. The latter mechanism has been found to govern the relaxation dynamics of the /sup 5/D/sub 2/, /sup 5/D/sub 1/ levels of europium, the /sup 5/D/sub 3/ level of terbium, the /sup 5/S/sub 2/ level of holmium and the /sup 2/D/sub 5/, /sup 1/G/sub 4/ and /sup 3/H/sub 4/ levels of thulium when the activator concentration amounts to several mol%.