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.

CRITICAL BEHAVIOR OF THE SPECIFIC HEAT IN THE VICINITY OF THE TRANSITION TEMPERATURE FOR S-TRIAZINE

2009 ◽  
Vol 23 (09) ◽  
pp. 2253-2259 ◽  
Author(s):  
M. KURT ◽  
H. YURTSEVEN
Keyword(s):  
Experimental Data ◽  
Phase Transition ◽  
Transition Temperature ◽  
Critical Exponent ◽  
Specific Heat ◽  
Power Law ◽  
Order Phase Transition ◽  
Critical Behavior ◽  
First Order ◽  
Second Order Phase Transition

The critical behavior of the specific heat is studied in s-triazine ( C 3 N 3 H 3). Using the experimental data for the CP, the temperature dependence of the specific heat is analyzed according to a power-law formula and the values of the critical exponent for CP are extracted in the vicinity of the transition temperature (TC=198.07 K ). It is indicated that s-triazine undergoes a weakly first order (quasi-continuous) or second order phase transition.

Size-dependent ultrahigh electrocaloric effect near pseudo-first-order phase transition temperature in barium titanate nanoparticles

RSC Advances ◽  
2015 ◽  
Vol 5 (47) ◽  
pp. 37476-37484 ◽  
Author(s):  
Hong-Hui Wu ◽  
Jiaming Zhu ◽  
Tong-Yi Zhang
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Order Phase Transition ◽  
Electrocaloric Effect ◽  
First Order ◽  
Size Dependent ◽  
First Order Phase Transition ◽  
Pseudo First Order ◽  
Barium Titanate Nanoparticles ◽  
First Order Phase

The proposed Pseudo-First-Order Phase Transition in a ferroelectric nanoparticle occurs at a temperature lower than its paraelectric/ferroelectric transition Curie temperature and is associated with an ultrahigh electrocaloric effect.

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.

Second-order Phase Transition Behavior in a Polymer above the Glass Transition Temperature

2021 ◽  
Author(s):  
Mitsuru Ishikawa ◽  
Taihei Takahashi ◽  
Yu-ichiro Hayashi ◽  
Maya Akashi ◽  
Takayuki Uwada
Keyword(s):  
Phase Transition ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Order Phase Transition ◽  
Second Order ◽  
Critical Slowing Down ◽  
Phase Transition Behavior ◽  
Slowing Down ◽  
Second Order Phase Transition

<p>Glass transition was primarily considered to be not phase transition; however, it has similarity to the second-order phase transition. Recent single-molecule spectroscopy developments have prompted re-investigating glass transition at the microscopic scale, revealing that glass transition includes phenomena similar to second-order phase transition. They are characterized by microscopic collective polymer motion and discontinuous changes in temperature dependent relaxation times, later of which is similar to critical slowing down, within a temperature window that includes the polymer calorimetric glass transition temperature. Considering that collective motion and critical slowing down are accompaniments to critical phenomena, second-order phase transition behavior was identified in polymer glass transition.</p>

Electro-optical Kerr effect of nematic mixtures comprised of 6CHBT and 6BOBT

2008 ◽  
Vol 16 (4) ◽  
Author(s):  
H. Tajalli ◽  
A. Ghanadzadeh ◽  
H. Khoshsima ◽  
P. Zhalefar
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Order Phase Transition ◽  
Linear Dependence ◽  
Kerr Effect ◽  
Optical Kerr Effect ◽  
Transition Temperatures ◽  
Phase Transition Temperatures ◽  
Good Agreement ◽  
Second Order Phase Transition

AbstractStatic Kerr effect and the pre-transition temperature were investigated for the 6CHBT, 6BOBT and the nematic mixtures, M1 (40% 6CHBT: 60% 6BOBT), M2 (30% 6CHBT: 70% 6BOBT) and M3 (20% 6CHBT: 80% 6BOBT) at temperatures above the nematic-isotropic transition temperature. The linear dependence of (T-T*)−1 on the Kerr constant is found to be in good agreement with the predications of the Landau-De Gennes model. The hypothetical second order phase transition temperatures and susceptibility values were determined for these compounds.

scholarly journals Second-order Phase Transition Behavior in a Polymer above the Glass Transition Temperature

2020 ◽  
Author(s):  
Mitsuru Ishikawa ◽  
Taihei Takahashi ◽  
Yu-ichiro Hayashi ◽  
Maya Akashi ◽  
Takayuki Uwada
Keyword(s):  
Phase Transition ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Single Molecule ◽  
Order Phase Transition ◽  
Collective Motion ◽  
Relaxation Times ◽  
Second Order ◽  
Second Order Phase Transition

Glass transition was primarily considered to be not phase transition; instead, regarded as pseudo secondorder phase transition due to its similarity to the ordinary second-order phase transition. Recent single-molecule spectroscopy developments have prompted re-investigating glass transition at the microscopic scale, confirming that the initial classification is correct and revealing that glass transition includes phenomena similar to second-order phase transition. They are characterized by microscopic collective polymer motion and discontinuous changes in temperature dependent relaxation times within a temperature window that includes the polymer calorimetric glass transition temperature. Generally, atom or molecule collective motion and discontinuous changes in physical quantities including relaxation times characterize critical phenomena associated with second-order phase transitions near specific temperatures. Thus, second-order phase transition phenomena are involved in polymer glass transition.

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