Rigid unit modes in framework silicates

1995 ◽  
Vol 59 (397) ◽  
pp. 629-639 ◽  
Author(s):  
Martin T. Dove ◽  
Volker Heine ◽  
Kenton D. Hammonds
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Transition Temperature ◽  
Low Energy ◽  
Soft Modes ◽  
Rigid Unit Modes

AbstractWe describe a model for framework silicates in which the SiO4 (and AlO4) tetrahedra are treated as perfectly rigid and freely jointed. From this model we are able to identify low-energy modes of distortion of the structure, which we call Rigid unit modes. These modes can act as soft modes to allow easy distortions at phase transition. We discuss three forces that will operate at a phase transition in conjunction with the candidate soft modes to determine which of the rigid unit modes will actually precipitate a phase transition, and illustrate these ideas by detailed discussions of the phase transitions in quartz, leucite and cristobalite. The model can also be used to estimate the transition temperature, and the theory highlights an important role for the stiffness of the tetrahedra.

Various types of holographic metal/superconductor phase transitions with dark matter sector

2016 ◽  
Vol 26 (06) ◽  
pp. 1750046
Author(s):  
Yan Peng ◽  
Tao Chen ◽  
Guohua Liu ◽  
Pengwei Ma
Keyword(s):  
Phase Transition ◽  
Black Hole ◽  
Dark Matter ◽  
Phase Transitions ◽  
Transition Temperature ◽  
De Sitter ◽  
Holographic Superconductor ◽  
Black Hole Background ◽  
Critical Phase ◽  
Matter Sector

We generalize the holographic superconductor model with dark matter sector by including the Stückelberg mechanism in the four-dimensional anti-de Sitter (AdS) black hole background away from the probe limit. We study effects of the dark matter sector on the [Formula: see text]-wave scalar condensation and find that the dark matter sector affects the critical phase transition temperature and also the order of phase transitions. At last, we conclude that the dark matter sector brings richer physics in this general metal/superconductor system.

scholarly journals The Effect of Selected Anions on Dipalmitoylphosphatidylcholine Phase Transitions

2002 ◽  
Vol 57 (7-8) ◽  
pp. 712-716 ◽  
Author(s):  
Adriana Przyczyna ◽  
Bożenna Różycka-Roszk ◽  
Marek Langner
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Transition Temperature ◽  
Phase Transition Temperature ◽  
Salt Concentration ◽  
Half Width ◽  
Main Phase ◽  
Interface Properties ◽  
Transition Enthalpy ◽  
Peak Half Width

The effect of three anions, Cl-, Br- and I-, on the phase transitions of dipalmitoylphosphatidylcholine (DPPC) was measured. Main phase transition was modestly affected by these anions in the salt concentration range 0.2 M. For Cl- and Br- the temperature of main phase transition was lower (by about 0.5 °C), its half-width modestly larger and enthalpy practically unchanged, all three parameters were altered to a much larger degree. Main phase transition temperature was 1.5 °C lower and the peak half-width significantly smaller. These changes were not accompanied by any alteration in main phase transition enthalpy. Iodide shifted the pretransition temperature toward lower values and increased its half-width to such an extent that at concentrations above 100 mm it was practically undetectable. Besides cations, the presence of anions also has a distinct effect on lipid bilayer interface properties.

Orientational Order Phase Transition in Solid C60

1997 ◽  
Vol 481 ◽  
Author(s):  
J. R. Soto ◽  
R. M. Valladares ◽  
A. Calles
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Vibrational Spectrum ◽  
Order Phase Transition ◽  
Effective Temperature ◽  
Phonon Spectrum ◽  
Molecular Orientation ◽  
Orientational Order ◽  
Low Energy ◽  
Thermal Parameters

ABSTRACTThe phonon spectrum and thermal parameters such as specific heat, effective temperature and amplitude of vibration of solid C60 are studied from ab-initio calculations. The relative orientations between the C60 balls are taken into account in a sc phase below 261.4K. The same properties are studied above the transition temperature (261.4K) where the balls are randomly oriented in a fcc structure. A difference is found in some of the thermal parameters due to the relative inter-molecular orientation. In particular, the low energy vibrational spectrum (which is separated by a ∼20meV gap from the intra-molecular spectrum) is changed.

Deuterium substitution effects on the structural and magnetic phase transitions of a hydrogen-bonded coordination polymer, bis(glycolato)copper(ii)

2016 ◽  
Vol 45 (42) ◽  
pp. 16774-16778 ◽  
Author(s):  
Shota Yoneyama ◽  
Takeshi Kodama ◽  
Koichi Kikuchi ◽  
Takumi Fujisawa ◽  
Akira Yamaguchi ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Transition Temperature ◽  
Magnetic Phase ◽  
Structural Phase ◽  
Magnetic Phase Transitions ◽  
Substitution Effects ◽  
Hydroxyl Groups ◽  
Large Shift ◽  
Deuterium Substitution

Bis(glycolato)copper(ii) [Cu(HOCH2CO2)2] shows a large shift of the structural phase transition temperature by deuterium substitution of the hydroxyl groups in it.

scholarly journals The GoogLeNet-assisted Phase Transition Detectors

2021 ◽  
Author(s):  
C. H. Wong ◽  
Raymond P. H. Wu ◽  
X. Lei ◽  
A. F. Zatsepin
Keyword(s):  
Phase Transition ◽  
Heat Capacity ◽  
Phase Transitions ◽  
Transition Temperature ◽  
Xy Model ◽  
Superconducting Transition ◽  
Superconducting Nanowires ◽  
Superconducting Vortices ◽  
Bkt Transition ◽  
Superconducting Nanowire

Abstract The GoogLeNet model can completely split the overlapped phase transitions in the superconducting nanowire arrays under Josephson interaction. In the presence of the phase fluctuations in superconducting nanowires array, the electrical resistance of the superconducting nanowires is always non-zero unless the system undergoes Berezinskii-Kosterlitz-Thouless (BKT) transition where the superconducting vortices and anti-vortices form pairs. The two-dimensional XY model can mimic the superconducting transition temperature Tc and the BKT transition temperature TBKT by observing the heat capacity anomalies upon cooling. If the Josephson coupling across the nanowires is strong, the heat capacity anomalies almost overlap with each other so that the traditional curve-fitting techniques are difficult to completely distinguish between the Tc and the TBKT. To solve this issue, we apply an artificial-intelligence technique to completely split the overlapped heat capacity anomalies. After the GoogLeNet-assisted phase transition detector is built, the GoogLeNet model can learn from the features of the phase transitions and then interpret the Tc and TBKT in the ‘unseen’ system precisely. Our work opens a path for the GoogLeNet model to enter the world of superconductivity.

scholarly journals Фазовая диаграмма и особенности поведения мягких мод в твердых растворах со структурой хантита TbFe-=SUB=-3-x-=/SUB=-Ga-=SUB=-x-=/SUB=-(BO_3)-=SUB=-4-=/SUB=-

2022 ◽  
Vol 130 (1) ◽  
pp. 84
Author(s):  
А.С. Крылов ◽  
А.Н. Втюрин ◽  
И.А. Гудим ◽  
И.В. Немцев ◽  
С.Н. Крылова
Keyword(s):  
Phase Transition ◽  
Phase Diagram ◽  
Phase Transitions ◽  
Raman Spectra ◽  
Solid Solutions ◽  
Structural Phase ◽  
Temperature Phase ◽  
Structural Phase Transitions ◽  
Soft Modes ◽  
Temperature Phase Diagram

The Raman spectra of four crystals of TbFe3-хGax (BO3) 4 solid solutions (x from 0 to 0.54) were studied in the temperature range from 8 to 350 K. The temperatures of structural phase transitions were determined. The observed spectral behavior is characteristic to condensation and restoration of soft modes. Soft modes are associated with a structural phase transition from the R32 phase to the P3121 phase. The Compositions-Temperature phase diagram was constructed

Multiple electrical phase transitions in nanocrystalline aluminium-substituted cobalt ferrite

2018 ◽  
Vol 32 (32) ◽  
pp. 1850358 ◽  
Author(s):  
Sweety Supriya ◽  
Sunil Kumar ◽  
Lagen Kumar Pradhan ◽  
Rabichandra Pandey ◽  
Manoranjan Kar
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Transition Temperature ◽  
Electrical Properties ◽  
Cobalt Ferrite ◽  
Ferroelectric Material ◽  
Relaxation Transition ◽  
Ferroelectric Materials ◽  
Transition Temperatures ◽  
Electrical Parameters

Electrical properties of a series of nanocrystalline aluminium-substituted cobalt ferrite CoAl[Formula: see text]Fe[Formula: see text]O4 (CAFO) with x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5 have been explored. The electrical parameters have been measured by employing impedance and techniques. The impedance has measured as a function of frequency and temperature for all the samples. The impedance increases with the increase in Al concentration in CAFO. Cobalt ferrite is yet to be verified as a ferroelectric material. However, the electrical properties reported here are similar to conventional ferroelectric materials. Multiple (two) electrical phase transitions have been observed, the two transition temperatures are identified as T[Formula: see text] and T[Formula: see text] i.e., one is dipole relaxation transition (T[Formula: see text]) and other one is electrical phase transition temperature. Both AC and DC measurements indicate the transition temperatures.

scholarly journals On Going to a New Era of Microgel Exhibiting Volume Phase Transition

Gels ◽  
2020 ◽  
Vol 6 (3) ◽  
pp. 26
Author(s):  
Haruma Kawaguchi
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Transition Temperature ◽  
Structural Analysis ◽  
Research Direction ◽  
Volume Phase Transition ◽  
New Era ◽  
Volume Phase ◽  
The World ◽  
Remarkable Progress

The discovery of phenomena of volume phase transition has had a great impact not only on bulk gels but also on the world of microgels. In particular, research on poly(N-isopropylacrylamide) (PNIPAM) microgels, whose transition temperature is close to body temperature, has made remarkable progress in almost 35 years. This review presents some breakthrough findings in microgels that exhibit volume phase transitions and outlines recent works on the synthesis, structural analysis, and research direction of microgels.

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