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1
Content available remote First-principles calculations of vibrational and thermodynamical properties of solids
100%
Parlinski K.
Materials Science Poland
|
2005
|
tom 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.
2
Content available remote Phonon-assisted tunneling through a quantum dot coupled to magnetic leads
100%
Rudziński W.
Materials Science Poland
|
2008
|
tom 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.
3
Content available remote Heat transfer in the plastic phases I and II of cyclopentane
100%
Konstantinov V. , Sagan V. , Revyakin V. , Karachevtseva A. , Pursky O.
Open Physics
|
2014
|
tom 12
|
nr 9
654-659
EN
Thermal conductivity of solid cyclopentane C5H10 has been measured at isochoric conditions in the plastic phases I and II for samples of different densities. Isochoric thermal conductivity is nearly constant in phase II and increases with temperature in phase I. Such behaviour is attributed to weakening of the translational orientational coupling which, in turn, leads to a decrease of phonon scattering on rotational excitations. The experimental data are described in terms of a modified Debye model of thermal conductivity with allowance for heat transfer by both low-frequency phonons and diffusive modes.
4
Content available remote Theoretical modelling of surface phonons
100%
Srivastava G. , Tütüncü H.
Open Physics
|
2009
|
tom 7
|
nr 2
209-219
EN
We present a mini review of progress made towards theoretical modelling of surface phonons. We outline the essential ingredients of two theoretical methods, viz. an adiabatic bond charge method for semiconductor surfaces and the ab-initio density-functional perturbation method for solid surfaces in general. From the results of theoretical calculations we establish trends and criteria for the existence of localized phonon modes on group-IV(001) and III-V(110) semiconductor surfaces. We further obtain signatures of characteristic vibrational modes which develop during dissociative molecular adsorption on Si(001) surfaces. The results are compared with available experimental measurements. Some remarks are forwarded regarding manipulation of surface phonon modes for scientific advances and technological applications.
5
Content available Structural Disorder in Quasicrystals
88%
Strzałka R. , Bugański I. , Śmietańska J. , Wolny J.
Archives of Metallurgy and Materials
|
2020
|
tom 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.
6
Content available remote First-principles investigation of structural, electronic, optical and dynamical properties in CsAu
88%
Erdinc B. , Soyalp F. , Akkus H.
Open Physics
|
2011
|
tom 9
|
nr 5
1315-1320
EN
The structural, electronic, optical and dynamical properties of CsAu compound in the CsCl(B2) phase were investigated using the density functional theory (DFT) within the generalized gradient approximation (GGA). The calculated lattice constant, static bulk modulus and first-order pressure derivative of the bulk modulus are reported and compared with previous experimental and theoretical calculations. The calculated electronic band structure for this compound is in good agreement with available theoretical and experimental studies. The present band calculation indicates that CsAu compound has an indirect gap at R→X points. Furthermore, the linear photon-energy-dependent dielectric functions have been calculated. For the first time, the electronic structure results are used, within the implementation of a linear-response technique, for calculations of phonon properties.
7
Content available remote First-principles LCAO study of phonons in NiWO4
88%
Kuzmin A. , Kalinko A. , Evarestov R.
Open Physics
|
2011
|
tom 9
|
nr 2
502-509
EN
The electronic, structural and phonon properties of antiferromagnetic wolframite-type NiWO4 have been studied using first-principles spin-polarized LCAO calculations based on the hybrid Hartree-Fock (HF)/density functional (DFT) scheme. The influence of different percentages of HF contribution, i.e. different correlation strength, on the structure and phonon frequencies has been investigated and compared with the available experimental data.
8
Content available remote The interval lattice Boltzmann method for transient heat transport
88%
Piasecka Belkhayat A.
Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej
|
2009
|
tom 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.
9
Content available remote Translation-rotation coupling and heat transfer in orientationally-disordered phase of CCl4
75%
Pursky O. , Konstantinov V.
Open Physics
|
2006
|
tom 4
|
nr 2
210-222
EN
The isochoric thermal conductivity of an orientationally-disordered phase of CCl4 is analysed within a model in which heat is transferred by phonons and above the phonon mobility edge by ”diffusive” modes migrating randomly from site to site. The mobility edge ω0 is found from the condition that the phonon mean-free path cannot become smaller than half the phonon wavelength. The contributions of phonon-phonon, one-, and two-phonon scattering to the total thermal resistance of solid CCl4 are calcualted under the assumption that the different scattering mechanisms contribute additively. An increase in the isochoric thermal conductivity with temperature is explained by suppression of phonon scattering at rotational excitations due to a decrease in correlation in the rotation of neighbouring molecules.
10
Content available Structural Disorder in Quasicrystals
75%
Strzałka R. , Bugański I. , Śmietańska J. , Wolny J. , Strzałka R. , Bugański I. , Śmietańska J. , Wolny J.
|
11
Content available remote Optical properties of fluoroindate glasses doped with rare earth ions.
63%
Gabryś-Pisarska J. , Żelechower M. , Pisarski W. A. , Gołąb S. , Bałuka M. , Ryba-Romanowski W.
Optica Applicata
|
2000
|
tom 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%.
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