Entropy diagnosis for phase transitions occurring in functional materials

2005 ◽  
Vol 77 (8) ◽  
pp. 1331-1343 ◽  
Author(s):  
Michio Sorai
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Selection Rule ◽  
Functional Materials ◽  
Condensed State ◽  
Molecular Motions ◽  
Good Tool ◽  
The Stability ◽  
Calorimetric Investigations ◽  
Good Probe

Functionalities of materials manifest themselves as the result of a concerted effect among molecular structure, intermolecular interactions, and molecular motions. Since the entropy of substance directly reflects the degree of molecular motions, the entropy plays a crucial role when one discusses the stability of a given phase at finite temperatures. When a delicate balance of these three factors is broken, the condensed state faces a catastrophe and is transformed into another phase. Therefore, phase transition is a good probe for elucidation of the interplay between these three factors. As there is no selection rule in thermodynamics, the entropy gain at the phase transition is a good tool to diagnose the mechanism of phase transition. In this presentation, calorimetric investigations aimed at the elucidation of the mechanisms governing phase transitions occurring in molecule-based functional materials are reviewed.

Phase transitions of BaCO3 at high pressures

2008 ◽  
Vol 72 (2) ◽  
pp. 659-665 ◽  
Author(s):  
S. Ono ◽  
J. P. Brodholt ◽  
G. D. Price
Keyword(s):  
Phase Transition ◽  
Experimental Study ◽  
High Pressure ◽  
Phase Transitions ◽  
Bulk Modulus ◽  
First Principles ◽  
High Pressures ◽  
Ambient Conditions ◽  
The Stability ◽  
Previous Experimental Study

AbstractFirst-principles simulations and high-pressure experiments were used to study the stability of BaCO3 carbonates at high pressures. Witherite, which is orthorhombic and isotypic with CaCO3 aragonite, is stable at ambient conditions. As pressure increases, BaCO3 transforms from witherite to an orthorhombic post-aragonite structure at 8 GPa. The calculated bulk modulus of the post-aragonite structure is 60.7 GPa, which is slightly less than that from experiments. This structure shows an axial anisotropicc ompressibility and the a axis intersects with the c axis at 70 GPa, which implies that the pressure-induced phase transition reported in previous experimental study is misidentified. Although a pyroxene-like structure is stable in Mg- and Ca-carbonates at pressures >100 GPa, our simulations showed that this structure does not appear in BaCO3.

Phase transition in decaying black holes

2020 ◽  
Vol 35 (31) ◽  
pp. 2050258
Author(s):  
Aloke Kumar Sinha
Keyword(s):  
Phase Transition ◽  
Black Holes ◽  
Black Hole ◽  
Phase Transitions ◽  
Quantum Black Hole ◽  
Dimensional Spacetime ◽  
The Stability ◽  
Derivatives Of ◽  
Physical Quantities ◽  
Thermal Stability Of

We had earlier derived the most general criteria for thermal stability of a quantum black hole, with arbitrary number of parameters, in any dimensional spacetime. These conditions appeared in form of a series of inequalities connecting second order derivatives of black hole mass with respect to its parameters. Some black holes like asymptotically flat rotating charged black holes do not satisfy all the stability criteria simultaneously, but do satisfy some of them in certain region of parameter space. They are known as “Quasi Stable” black holes. In this paper, we will show that quasi stable black holes although ultimately decay under Hawking radiation undergo phase transitions. These phase transitions are different from phase transition in ADS Schwarzschild black hole. These are marked by sign changes in certain physical quantities apart from specific heat of the black hole. We will also discuss the changes in the nature of fluctuations of the parameters of these quasi stable black holes with different phases.

81Br and 127I NQR and Phase Transitions in CH3NH3 HgBr3 and CH3NH3 HgI3

1990 ◽  
Vol 45 (3-4) ◽  
pp. 343-348 ◽  
Author(s):  
Hiromitsu Terao ◽  
Tsutomu Okuda
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Large Amplitude ◽  
Molecular Motions ◽  
Temperature Variations ◽  
Halogen Atoms ◽  
Resonance Frequencies ◽  
Successive Phase

Abstract The 81Br and 127I NQR spectra were recorded in CH3NH3 HgBr3 and CH3NH HgI3 , respectively. In addition to a phase transition at 338 K, successive phase transitions take place at 127 ± 1, 184±1 and 243±5 K in CH3NH3 HgBr3. On heating, the resonance lines of CH3NH3HgI3 disappear near a phase transition at 328 K and one line appears above this temperature. The temperature variations of the resonance frequencies of the terminal halogen atoms in both crystals are extraordinarily steep. This indicates the large amplitude molecular motions expected for the CH3NH3 cations which are linked to the terminal halogen atoms through N-H ··· X type H-bonding.

scholarly journals Holographic subregion complexity in metal/superconductor phase transition with Born–Infeld electrodynamics

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
Yu Shi ◽  
Qiyuan Pan ◽  
Jiliang Jing
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Critical Temperature ◽  
Inflection Point ◽  
Entanglement Entropy ◽  
Superconducting Phase ◽  
Holographic Entanglement Entropy ◽  
Good Probe

AbstractWe investigate the holographic subregion complexity (HSC) and compare it with the holographic entanglement entropy (HEE) in the metal/superconductor phase transition for the Born–Infeld (BI) electrodynamics with full backreaction. Based on the subregion CV conjecture, we find that the universal terms of HSC remain finite during phase transitions, and the HSC is a good probe to the critical temperature in the holographic superconducting system. Furthermore, we observe that for the operator $$\mathcal {O}_{+}$$ O + , the HSC of the superconducting phase decreases first and then increases as the BI parameter increases, which is completely different from that of HEE, and the value of the BI parameter corresponding to the inflection point of HSC is larger than that of HEE. But for the operator $$\mathcal {O}_{-}$$ O - , the HSC increases monotonically as the BI parameter increases, which is similar to that of HEE.

Symmetry relationship in electron beam induced phase transitions

1989 ◽  
Vol 47 ◽  
pp. 500-501
Author(s):  
J. P. Zhang ◽  
L. D. Marks
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Oxygen Content ◽  
Transition Metal Oxides ◽  
Selection Rule ◽  
Point Group ◽  
Group Symmetry ◽  
Lower Oxygen ◽  
Image Position ◽  
New Phase

In this work we present a symmetry rule for the phase transitions in transition metal oxides driven by DIET of oxygen in an electron microscope. The phase transitions are to a structure with a higher point group symmetry. The new phase with a lower oxygen content is either one with a supergroup symmetry with respect to the original phase, or an amorphous intermediary. If a possible lower oxygen content phase does not have the correct supergroup symmetry, it is not formed. Of this type are the phase transitions in TiO2, MoO3, WO3, V2O5 and Ta2o5 of which the experimental results are listed in the first section of Table 1. It is also found that the point group is conserved during the phase transition if the oxide belongs to the highest groups Oh or D6h, for instance NiO, CoO and ZnO. This symmetry selection rule can therefore be used to predict the route of the phase transition. The selection rule is:

scholarly journals High-Temperature-Induced Phase Transitions in Honeycomb Layered Oxides A2Ni2TeO6 (A = Na, K)

2020 ◽  
Author(s):  
Josef Rizell ◽  
Godwill Mbiti Kanyolo ◽  
Titus Masese ◽  
Yasmine Sassa ◽  
Zhen-Dong Huang
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Structural Changes ◽  
Short Communication ◽  
Hexagonal Lattice ◽  
Functional Materials ◽  
Temperature Elevation ◽  
Layered Oxides ◽  
X Ray Diffraction ◽  
X Ray

<p><b>Phase transitions have been surmised as underlying factors behind the </b><b>exceptional electrochemical, ionic and magnetic functionalities that have catapulted honeycomb layered oxides as superb functional materials. As such, in this study (<i>short communication</i>), we explore temperature elevation as an avenue for inducing phase transitions in </b><b>h</b><b>oneycomb layered oxides adopting the composition </b><b><i>A</i></b><b><sub>2</sub></b><b><i>M</i></b><b><sub>2</sub></b><b>TeO<sub>6</sub> (<i>A </i>= Li, Na, K; <i>M</i> = (transition) metal). X-ray diffraction analyses indicate structural changes occurring in Na<sub>2</sub>Ni<sub>2</sub>TeO<sub>6 </sub>hexagonal lattice (centrosymmetric <i>P</i>6<sub>3</sub>/<i>mcm </i>→ accentric <i>P</i>6<sub>3</sub>(22) space group) with increase in temperature, whilst in the potassium homologue (K<sub>2</sub>Ni<sub>2</sub>TeO<sub>6</sub>), the phase transitions entail multiple changes in the lattice (from the initial hexagonal → monoclinic (pseudo-orthorhombic) lattice at intermediate temperatures) which reverts back to its initial hexagonal lattice with further increase in temperatures. This study opens an alternative channel for generating phase transition beside electrochemical alkali (re)insertion. </b><b></b></p>

scholarly journals High-Temperature-Induced Phase Transitions in Honeycomb Layered Oxides A2Ni2TeO6 (A = Na, K)

2020 ◽  
Author(s):  
Josef Rizell ◽  
Godwill Mbiti Kanyolo ◽  
Titus Masese ◽  
Yasmine Sassa ◽  
Zhen-Dong Huang
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Structural Changes ◽  
Short Communication ◽  
Hexagonal Lattice ◽  
Functional Materials ◽  
Temperature Elevation ◽  
Layered Oxides ◽  
X Ray Diffraction ◽  
X Ray

<p><b>Phase transitions have been surmised as underlying factors behind the </b><b>exceptional electrochemical, ionic and magnetic functionalities that have catapulted honeycomb layered oxides as superb functional materials. As such, in this study (<i>short communication</i>), we explore temperature elevation as an avenue for inducing phase transitions in </b><b>h</b><b>oneycomb layered oxides adopting the composition </b><b><i>A</i></b><b><sub>2</sub></b><b><i>M</i></b><b><sub>2</sub></b><b>TeO<sub>6</sub> (<i>A </i>= Li, Na, K; <i>M</i> = (transition) metal). X-ray diffraction analyses indicate structural changes occurring in Na<sub>2</sub>Ni<sub>2</sub>TeO<sub>6 </sub>hexagonal lattice (centrosymmetric <i>P</i>6<sub>3</sub>/<i>mcm </i>→ accentric <i>P</i>6<sub>3</sub>(22) space group) with increase in temperature, whilst in the potassium homologue (K<sub>2</sub>Ni<sub>2</sub>TeO<sub>6</sub>), the phase transitions entail multiple changes in the lattice (from the initial hexagonal → monoclinic (pseudo-orthorhombic) lattice at intermediate temperatures) which reverts back to its initial hexagonal lattice with further increase in temperatures. This study opens an alternative channel for generating phase transition beside electrochemical alkali (re)insertion. </b><b></b></p>

scholarly journals Electric properties of olive oil under pressure

2021 ◽  
Author(s):  
L. T. Pawlicki ◽  
R. M. Siegoczyński ◽  
S. Ptasznik ◽  
K. Marszałek
Keyword(s):  
Molecular Structure ◽  
Phase Transition ◽  
Phase Diagram ◽  
Phase Transitions ◽  
Olive Oil ◽  
Material Parameters ◽  
First Order ◽  
Long Time ◽  
Capacitive Reactance ◽  
First Order Phase

AbstractThe main purpose of the experiment was a thermodynamic research with use of the electric methods chosen. The substance examined was olive oil. The paper presents the resistance, capacitive reactance, relative permittivity and resistivity of olive. Compression was applied with two mean velocities up to 450 MPa. The results were shown as functions of pressure and time and depicted on the impedance phase diagram. The three first order phase transitions have been detected. All the changes in material parameters were observed during phase transitions. The material parameters measured turned out to be the much more sensitive long-time phase transition factors than temperature. The values of material parameters and their dependence on pressure and time were compared with the molecular structure, arrangement of molecules and interactions between them. Knowledge about olive oil parameters change with pressure and its phase transitions is very important for olive oil production and conservation.

Room-temperature NaI/H2O compression icing: solute–solute interactions

2017 ◽  
Vol 19 (39) ◽  
pp. 26645-26650 ◽  
Author(s):  
Qingxin Zeng ◽  
Chuang Yao ◽  
Kai Wang ◽  
Chang Q. Sun ◽  
Bo Zou
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Bond Energy ◽  
Room Temperature ◽  
Solute Concentration ◽  
Solute Interaction ◽  
Solute Interactions

H–O bond energy governs the PCx for Na/H2O liquid–VI–VII phase transition. Solute concentration affects the path of phase transitions differently with the solute type. Solute–solute interaction lessens the PC2 sensitivity to compression. The PC1 goes along the liquid–VI boundary till the triple phase joint.

scholarly journals The origin of the lattice thermal conductivity enhancement at the ferroelectric phase transition in GeTe

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Đorđe Dangić ◽  
Olle Hellman ◽  
Stephen Fahy ◽  
Ivana Savić
Keyword(s):  
Phase Transition ◽  
Thermal Conductivity ◽  
Phase Transitions ◽  
Thermoelectric Materials ◽  
Ferroelectric Phase Transition ◽  
Lattice Thermal Conductivity ◽  
Ferroelectric Phase ◽  
Structural Phase ◽  
High Symmetry ◽  
Structural Phase Transitions

AbstractThe proximity to structural phase transitions in IV-VI thermoelectric materials is one of the main reasons for their large phonon anharmonicity and intrinsically low lattice thermal conductivity κ. However, the κ of GeTe increases at the ferroelectric phase transition near 700 K. Using first-principles calculations with the temperature dependent effective potential method, we show that this rise in κ is the consequence of negative thermal expansion in the rhombohedral phase and increase in the phonon lifetimes in the high-symmetry phase. Strong anharmonicity near the phase transition induces non-Lorentzian shapes of the phonon power spectra. To account for these effects, we implement a method of calculating κ based on the Green-Kubo approach and find that the Boltzmann transport equation underestimates κ near the phase transition. Our findings elucidate the influence of structural phase transitions on κ and provide guidance for design of better thermoelectric materials.

Sign in / Sign up

Export Citation Format

Share Document