Full-text resources of PSJD and other databases are now available in the new Library of Science.
Visit https://bibliotekanauki.pl
Preferences help
Polish version English version Language
enabled [disable] Abstract
Number of results

Results found: 5

Number of results on page
first rewind previous Page / 1 next fast forward last

Search results

Search:
in the keywords:  64.70.Rh
help Sort By:

help Limit search:
first rewind previous Page / 1 next fast forward last
1
Content available remote

Phase Diagrams of Crystals with One-Dimensional Modulated Phases Induced by 2d Active Representations

100%
Sikora R.
Acta Physica Polonica A
|
1994
|
vol. 86
|
issue 6
955-968
EN
A one-dimensional model of particles with a displacive degree of freedom for crystals possessing incommensurate phases which arise as a result of the condensation of either real two-dimensional or complex one-dimensional irreducible representations, has been proposed. For these representations all invariants of the free energy expansion can be divided to four general forms. For the active irreducible representations for which the invariants belong to the first form a complete list of invariants is derived. In this case the incommensurate modulation propagates along the symmetry axis and for such crystals a proposed one-dimensional model may be a good approach to describe the main features of the devil's staircase curve. The particles of the model interact with harmonic and anharmonic terms. The last ones may contain an additional third order term provided a soft phonon branch has a symmetry τ^{1}. The calculated phase diagrams show sequences of the incommensurate and commensurate one-dimensional phases. In the presence of the third order anharmonic term the incommensurate phase proves to be stable closer to the phase boundary to the normal phase.
2
Publication available in full text mode
Content available

Rayleigh Scattering of Mössbauer Radiation Method Used in Dynamics Studies of Condensed Matter

51%
Enescu S., Bibicu I.
Acta Physica Polonica A
|
2005
|
vol. 107
|
issue 3
479-489
EN
The Rayleigh scatte ring of the Mössbauer radiation is a less common technique used in the study of the properties of condensed matter. The detection of the scattered radiation via the nuclear resonance absorption, with an energy resolution of the order of 10^{-8} eV makes this technique very sensitive to dynamics changes. The results of our studies by the Rayleigh scattering of the Mössbauer radiation on pyrolytic graphite (C) and rubidium tetrachlorozincate (Rb_2ZnCl_4) are reported. The contribution of the coherent inelastic scattering to the total intensity in C(002) is presented like a consequence of the coupling motions of C atoms in the hexagonal plane. The normal-incommensurate phase transition in Rb_2ZnCl_4 is discussed in connection with the photon-phonon interaction.
3
Content available remote

Phase Transitions in [N(CH_3)_4]_2ZnCl_4 and [N(CH_3)_4]_2CuCl_4 Crystals Related with the Incommensurate Modulation Existence

51%
Sveleba S., Semotyuk O., Katerynchuk I., Kunyo I., Karpa I., Pankivskyi Y.
Acta Physica Polonica A
|
2008
|
vol. 114
|
issue 4
791-806
EN
The continuous phase transitions are observed in the crystals with incommensurate phase. They are transitions of parent-incommensurate phases (T_i); transitions between metastable states; incommensurate-commensurate phases (T_c). It was set that phase transition between parent and incommensurate phase is a continuous second-order phase transition with a critical index β = 0.5. The transition between metastable states is a continuous phase transition through the intermediate temperature region - incommensurate phase. The wave vector changes with the temperature here and wave vectorwe q* = q₁ - q₂ appears, where q₁, q₂ denote commensurate values of incommensurability wave vector of neighboring metastable states. It was shown that the phase transition between incommensurate and commensurate phases is a continuous phase transition.
4
Publication available in full text mode
Content available

The Stochastic Mode of the Modulated Structure in [N(CH_3)_4]_2MeCl_4 Dielectric Crystals

51%
Sveleba S., Semotyuk O., Katerynchuk I., Furgala Y., Pankivskyi Y.
Acta Physica Polonica A
|
2006
|
vol. 109
|
issue 6
695-700
EN
Temperature behavior of the optical birefringence in the transitional regions of the incommensurate phase of [N(CH_3)]CuCl_4 was studied. Temperature dependencies of the modulated structure wave vector and of the specific heat in these regions were analyzed. The stochastic mode of the incommensurate modulated structure in [N(CH_3)]MeCl_4 (Me = Cu, Fe) dielectric crystals was discovered.
5
Content available remote

Phenomenological Versus Microscopic Interpretation of Incommensurate Systems -BCCD and the ANNNI-Model

51%
Schaack G.
|
EN
Phenomenological and microscopic models to treat modulated crystal structures are reviewed. Their applicability to interpret the specific phase diagram of betaine-calciumchloride-dihydrate (BCCD), which is of the "incomplete devils,s staircase" type, is critically discussed. Some experimental observations, which emphasize the fractal topology of the BCCD phase diagram, have been compiled. They support the preference of microscopic approaches as the ANNNI-model over the classic Landau theory for this specific case.
first rewind previous Page / 1 next fast forward last
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.