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1

Phase Transitions in Fe-Rh Alloys Induced by Temperature

100%

Rodionov V., Rodionova V., Annaorazov M.

Acta Physica Polonica A

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2015

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vol. 127

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issue 2

445-447

EN

This research work was aimed to find the composition of equiatomic Fe-Rh alloy and to find the way of preparation of samples with extremely narrow thermal hysteresis and repeatable results. Alloys with content of Fe from 48 up to 52 at.% were examined. Fe-Rh alloys were prepared in forms of bulk piece, plate and wire. The plates of alloys were found to be more perspective for further investigations. The influence of parameters of ingot and samples treatments on antiferromagnetic-ferromagnetic transition was studied. The ways of narrowing of temperature hysteresis were established.

2

Ferroelastic Phase Transition in a Layered Bismuth Oxychloride Single Crystals

100%

Bunda V., Bunda S., Vashchuk F., Feher A., Kajňaková M., Kováč J., Syrkin E.

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issue 5

1069-1070

EN

We report the results of low-temperature specific-heat, magnetization, and X-ray diffraction measurements on a bismuth oxyhalide (BiOCl) single crystal. We conclude that BiOCl in temperature region 150-230 K shows "antiferroelastic-paraelectric" phase transitions at critical temperatures T_{c1} = 167.5 K and T_{c2} = 214.6 K, respectively.

3

TBI Calculations of the Elastic Properties and Structural Phase Transformation in Novel Materials: Yttrium Nitride

100%

Singh S., Chauhan R., Gour A.

Acta Physica Polonica A

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2011

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vol. 120

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issue 6

1021-1025

EN

We have carried out high pressure theoretical structural studies of yttrium nitride to examine the phase transition phenomena from the NaCl structure to CsCl structure by using a three-body potential model. The phase transition pressure (140 GPa) predicted by this approach is close to the phase transition pressure, predicted by others (138 GPa). Yttrium nitride is a novel and less explored material. Under high pressure yttrium nitride goes through a sudden collapse in volume showing the first order phase transition. To understand the effect of pressure we studied bulk properties, elastic constants and their combination. The pressure volume equation of state provides meaningful signatures of physical and chemical phenomena under high pressure. Moreover we have successfully checked the stability criterion for this compound.

4

PIPT from the Beginning to Future

100%

Cailleau H., Luty T., Koshihara S., Servol M., Lorenc M., Buron-Le Cointe M., Collet E.

Acta Physica Polonica A

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2012

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vol. 121

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issue 2

297-306

EN

The birth of the field of photoinduced phase transitions was strongly influenced by the conceptual viewpoint expressed by Professor Y. Toyozawa on the condensation of relaxed excitons. Since this first period, twenty years ago, this young field has been expanding rapidly along a diversity of directions. Nowadays, it goes hand in hand with the challenges of today's science: emergence, nonlinearity, coherence, far away from equilibrium, for example. The control of the functionality of a material via photoexcited states poses many new fundamental questions. Some of them will be overviewed: (i) the nature of the control parameters and the nature of the relevant collective variables, especially the order parameters, which characterize the evolution of the system, (ii) the difference between photoinduced transformations under continuous light irradiation and those resulting from an ultrashort laser pulse, (iii) the physical mechanisms of ultrafast photoinduced phase transitions from the formation and proliferation of phototransformed entities to the softening of a collective mode.

5

Phonon Dispersion Analysis as an Indispensable Tool for Predictions of Solid State Polymorphism and Dynamic Metastability: Case of Compressed Silane

100%

Kurzydłowski D., Grochala W.

Acta Physica Polonica A

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2011

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vol. 119

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issue 6

895-900

EN

Diamond anvil cell experiments suggest that upon compression above 26.5 GPa silane (SiH_4) forms a polymeric phase VI, whose crystal structure has not yet been solved. Here we present DFT calculations showing how phonon-guided optimization leads to a polymeric Fdd2 structure which is the lowest-enthalpy polymorph of SiH_4 above 26.8 GPa, and which most probably can be identified as the experimentally observed polymeric phase. The new algorithm of predicting the lowest-energy structures enables simultaneous inspection of the potential energy surface of a given system, calculation of its vibrational properties, and assessment of chances for obtaining a metastable ambient-pressure structure via decompression. Our calculations indicate that at room temperature the differences in the vibrational and entropy terms contributing to the Gibbs free energy of different polymorphs of silane are negligible in comparison with corresponding differences in the zero-point energy corrections, in contrast to earlier suggestions. We also show that the Fdd2 polymorph should be metastable upon decompression up to 5 GPa, which suggests the possibility of obtaining a polymeric ambient-pressure form of SiH_4. Polymeric silane should exhibit facile thermal decomposition with evolution of molecular hydrogen and thus constitute an efficient (12.5 wt%) material for hydrogen storage.

6

High-Pressure Study of Gd_2(MoO_4)_3 by Raman Scattering and Ab Initio Calculations

100%

Lucazeau G., Bouvier P., Pasturel A., Le Bacq O., Pagnier T.

Acta Physica Polonica A

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2009

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vol. 116

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issue 1

25-31

EN

High-pressure induced phase transitions in a single crystal of gadolinium molybdate, Gd_2(MoO_4)_3 were studied by the Raman spectroscopy and ab initio calculations. The amorphization of the sample takes place at about 6 GPa in a mixture of alcohol as a pressure transmitting medium and begins as soon as 3 GPa in argon. In both media, the amorphization is irreversible in the 0-9 GPa investigated pressure range. The joint ab initio and Raman results allowed us to conclude that rotations of MoO_4 tetrahedra are the primary structural changes involved in the first phase transition (at about 2 GPa) explaining the softening of the low frequency modes at about 50 cm^{-1}. In addition, a progressive distortion of tetrahedra followed by a coordination change (IV-VI) of Mo atoms is observed through the five structural transitions including amorphization. This mechanism based on the steric hindrance of polyhedra is believed to be the most relevant for explaining the amorphization of Gd_2(MoO_4)_3.

7

Molecular Reorientations οf N-n-Hexyltetrachlorophthalimide Studied by ^1H NMR

88%

Hołderna-Natkaniec K., Jurga K., Woźniak-Braszak A., Walczak A.

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issue 4

537-548

EN

The spin-lattice relaxation times T_{1} and the second moment of ^{1}H NMR line have been employed to study the internal dynamics of protons of N-n-hexyl-tetra-chloro-phthali-mides in the temperature range 80-350 K. The model of internal reorientations has been proposed.

Refine search results

Phase Transitions in Fe-Rh Alloys Induced by Temperature

Ferroelastic Phase Transition in a Layered Bismuth Oxychloride Single Crystals

TBI Calculations of the Elastic Properties and Structural Phase Transformation in Novel Materials: Yttrium Nitride

PIPT from the Beginning to Future

Phonon Dispersion Analysis as an Indispensable Tool for Predictions of Solid State Polymorphism and Dynamic Metastability: Case of Compressed Silane

High-Pressure Study of Gd_2(MoO_4)_3 by Raman Scattering and Ab Initio Calculations

Molecular Reorientations οf N-n-Hexyltetrachlorophthalimide Studied by ^1H NMR