NQR, DSC, and X-Ray Structure Studies of Pyridinium Tetrabromozincate and Pyridinium Tetrabromocadmate (C5H5NH)2MBr4 · nH2O (M = Zn and Cd; n = 0, 1); Phase Transitions and Weak Hydrogen Bond Interactions

Crystals of pyridinium tetrabromozincate and pyridinium tetrabromocadmate were obtained as monohydrates and anhydrous compounds. The crystal structure of metastable (C5H5NH)2- CdBr4・H2O was determined at 300(2) K; triclinic space group P1̄ with a = 7.875(2), b = 8.151(1), and c = 16.356(2) Å, α = 79.260(10), β = 86.030(10), and γ = 61.440(10)°, Z = 2. All compounds except for stable (C5H5NH)2CdBr4・H2O gave four 81Br NQR lines at temperatures between 77 and around 325 K. The stable (C5H5NH)2CdBr4・H2O undergoes a first-order phase transition at TC = 116 K. Four 81Br NQR lines below TC merged into two with equal intensities above TC, indicating a 180° flip motion of water molecules in the r. t. phase. The 81Br NQR lines of the two anhydrous compounds faded out around 325 K probably due to the reorientational motion of ZnBr42− or CdBr42− ions. The respective two 81Br NQR lines of the hydrates exhibited anomalous positive temperature dependence. This is considered to be induced by a weakening in the interionic C-H・・・Br hydrogen bonds with increasing temperature. The DSC measurements of the anhydrous compounds have revealed phase transitions above r. t. The thermal behavior of (C5H5NH)2CdBr4 is complicated by the formation of metastable forms.

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Theory of Photoinduced Phase Transitions: From Semiclassical to Quantum Aspects

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.112.21 ◽

2006 ◽

Vol 112 ◽

pp. 21-38

Author(s):

Tetsuo Ogawa

Keyword(s):

Phase Transitions ◽

Excited States ◽

Domain Walls ◽

Particle Density ◽

Structural Phase ◽

Electron Hole ◽

One Dimensional ◽

First Order Phase Transition ◽

New Material ◽

First Order Phase

We review recent progress of theoretical studies for the photoinduced phase tran- sitions (PIPTs) to clarify what the PIPTs are. There are two types of the PIPTs: (a) global change via optically excited states and (b) new material phase creation in optically excited states. First, concerning (a), photoinduced structural phase transitions via excited electronic states are discussed using a minimal one-dimensional model composed of localized electrons and lattices. We show that the global structural change by photoexcitation only at a single site is possible under the adiabatic or diabatic approximation. This dynamics of the domain bound- aries (domain walls) is called the “photoinduced domino process,” which is the photoinduced nucleation in nonequilibrium first-order phase transition. Second, concerning (b), we discuss quantum orders of electron-hole (e-h) systems, which are optically excited states of insulators consisting of many electrons and holes in two bands. In particular, the “exciton Mott transi- tion,” i.e., the “from-insulator-to-metal” transition of the e-h systems as the particle density increases is introduced. We stress that this transition depends strongly on dimensionality of the system.

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OBSERVATION OF PHASE TRANSITIONS AT THE (100) SURFACE OF Al-3 at.% Ag

Surface Review and Letters ◽

10.1142/s0218625x95000133 ◽

1995 ◽

Vol 02 (02) ◽

pp. 141-145 ◽

Cited By ~ 1

Author(s):

E. WETLI ◽

M. HOCHSTRASSER ◽

D. PESCIA ◽

M. ERBUDAK

Keyword(s):

Phase Transition ◽

Phase Transitions ◽

Photoelectron Spectroscopy ◽

Short Range ◽

Short Range Order ◽

Elevated Temperatures ◽

X Ray ◽

First Order ◽

First Order Phase Transition ◽

First Order Phase

In the bulk binary alloy Al-3 at.% Ag , Ag 2 Al precipitates are formed below 410°C which are reversibly dissolved at elevated temperatures. We have followed this phase transition at a (100) surface as a function of temperature by monitoring the bandwidth of the Ag 4d states in X-ray photoelectron spectroscopy. Since the bandwidth measures the coordination number of the emitting atoms, it directly reveals the short-range order of the Ag atoms at the surface. The measurements show that the dissolution of the Ag -rich clusters starts at temperatures at least 100 K below the bulk transition, and the observed hysteresis behavior is indicative of a first-order phase transition at the surface.

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Effect of Alkyl Chain Length of Alcohols on Cholesteric Uniaxial to Cholesteric Biaxial Phase Transitions in a Potassium Laurate/Alcohol/Potassium Sulfate/Water/Brucine Lyotropic Mixture: Evidence of a First-Order Phase Transition

The Journal of Physical Chemistry B ◽

10.1021/jp310981d ◽

2013 ◽

Vol 117 (3) ◽

pp. 942-948 ◽

Cited By ~ 16

Author(s):

Dennys Reis ◽

Erol Akpinar ◽

Antônio Martins Figueiredo Neto

Keyword(s):

Phase Transition ◽

Phase Transitions ◽

Order Phase Transition ◽

Alkyl Chain ◽

Alkyl Chain Length ◽

Potassium Sulfate ◽

First Order ◽

Potassium Laurate ◽

First Order Phase Transition ◽

First Order Phase

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GRAVITATIONAL WAVES FROM COSMOLOGICAL PHASE TRANSITIONS

International Journal of Modern Physics A ◽

10.1142/s0217751x09044966 ◽

2009 ◽

Vol 24 (08n09) ◽

pp. 1541-1544

Author(s):

ARIEL MÉGEVAND

Keyword(s):

Phase Transition ◽

Phase Transitions ◽

Gravitational Waves ◽

Order Phase Transition ◽

Gravitational Radiation ◽

First Order ◽

First Order Phase Transition ◽

First Order Phase

I discuss the gravitational radiation produced in a first-order phase transition due to the turbulence that is caused by bubble expansion. I compare the cases of deflagration and detonation bubbles.

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Phase transitions and topological defects

10.1093/oso/9780198802877.003.0016 ◽

2018 ◽

Author(s):

Michael Kachelriess

Keyword(s):

Phase Transition ◽

Phase Transitions ◽

Early Universe ◽

Topological Defects ◽

False Vacuum ◽

First Order ◽

Broken Symmetries ◽

First Order Phase Transition ◽

True Vacuum ◽

First Order Phase

As the early universe cools down, it may perform transitions to phases with more and more broken symmetries. In a first-order phase transition, fields may be trapped in the false vacuum; the rate of the resulting tunneling process to the true vacuum is derived. Phase transitions can lead also to the formation of topological defects. Their structure and the reason for their stability are discussed.

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Modeling of Phase Transitions Kinetics in Systems with Two Interacting Order Parameters

Materials Science Forum ◽

10.4028/www.scientific.net/msf.845.166 ◽

2016 ◽

Vol 845 ◽

pp. 166-169 ◽

Cited By ~ 1

Author(s):

Dmitry A. Kuzmin ◽

Igor V. Bychkov ◽

Ivan Yu. Biryukov ◽

Alexander P. Kamantsev ◽

Victor V. Koledov ◽

...

Keyword(s):

Phase Transition ◽

Phase Transitions ◽

Order Phase Transition ◽

Transition Process ◽

Order Parameters ◽

First Order ◽

First Order Phase Transition ◽

1D Model ◽

Coupled Solution ◽

First Order Phase

We present common 1D model of first order phase transition based on coupled solution of order parameters evolution and heat transfer equations. Such a model may be used for simulation of phase transitions in multiferroics or magnetostructural phase transitions, for example. First order phase transition process has been described by Landau-Khalatnikov-like equation with the thermodynamic potential of 2-3-4 and 2-4-6 types.

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Structure and Phase Transition of [(CH2OH)3CNH3]2SiF6

Zeitschrift für Naturforschung A ◽

10.1515/zna-2003-2-308 ◽

2003 ◽

Vol 58 (2-3) ◽

pp. 121-125 ◽

Cited By ~ 8

Author(s):

B. Kosturek ◽

Z. Czapla ◽

A. Waskowska

Keyword(s):

Phase Transition ◽

Optical Observations ◽

Linear Birefringence ◽

Temperature Phase ◽

Scanning Calorimetry ◽

Dsc Measurements ◽

First Order Phase Transition ◽

Cell Dimensions ◽

Unit Cell Dimensions ◽

First Order Phase

Single crystals of (TRIS)2SiF6 were grown and characterised by X-ray analysis, differential scanning calorimetry (DSC) and optical investigations. They were bond to be trigonal, space group P3̅, with the unit cell dimensions a = 7.699(1), c = 7.818(2) Å . The SiF2-6 anions, located in large cavities formed by hydrogen bonded cations, are strongly disordered at room temperature. The DSC measurements revealed a first-order phase transition at TC ≈ 177 K with a hysteresis of 4 K. The nature of the transition was confirmed by a sharp increase of the linear birefringence below TC. Optical observations under a polarizing microscope showed a domain structure of the low temperature phase, characteristic of ferroelastic materials

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WEIGHT RATIO FIXING AT FIRST ORDER PHASE TRANSITIONS

International Journal of Modern Physics C ◽

10.1142/s0129183192000737 ◽

1992 ◽

Vol 03 (05) ◽

pp. 1109-1117

Author(s):

THOMAS LIPPERT ◽

KLAUS SCHILLING ◽

PEER UEBERHOLZ ◽

GYAN BHANOT

Keyword(s):

Phase Transition ◽

Phase Transitions ◽

Weight Ratio ◽

Phenomenological Method ◽

Reliable Determination ◽

First Order ◽

First Order Phase Transition ◽

Two Phases ◽

First Order Phase

The presence of strong metastabilities in computer simulations of models showing a first order phase transition hinders a reliable determination of the weight ratio between the two phases. We discuss a new phenomenological method which allows an accurate fixing of the weight ratio using the standard multihistogram procedure.

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Phase Transitions in 3D Site-Diluted Potts Model with Spin States q=4

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.168-169.357 ◽

2010 ◽

Vol 168-169 ◽

pp. 357-360 ◽

Cited By ~ 5

Author(s):

Akai K. Murtazaev ◽

A.B. Babaev ◽

G.Ya. Aznaurova

Keyword(s):

Phase Transition ◽

Phase Transitions ◽

Order Phase Transition ◽

Potts Model ◽

Finite Size ◽

Critical Parameters ◽

Spin States ◽

Spin Concentration ◽

First Order Phase Transition ◽

First Order Phase

We study the phase transitions and critical phenomena in 3D site-diluted (with nonmagnetic impurities) Potts model with spin states q=4 by Monte-Carlo method. The systems with linear sizes L=20-32 and spin concentrations p=1.00, 0.90, 0.65 are examined. Using the Binder cumulants method the forth order it is shown that the second-order phase transition is observed in strongly diluted model at spin concentration p=0.65; the pure model (p=1.00) and weakly diluted one (p=0.90) reveals the first-order phase transition. On the basis of finite-size scaling theory the static critical parameters of heat capacity, susceptibility, magnetization, and correlation length exponent are calculated.

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Research of Changes of Value of Potential Barrier at the Metal/Polymer Interface during Phase Transitions in Metal

Materials Science Forum ◽

10.4028/www.scientific.net/msf.845.61 ◽

2016 ◽

Vol 845 ◽

pp. 61-64

Author(s):

Pavel Chernov ◽

Aleksandr Ponomarev ◽

Aleksei N. Lachinov

Keyword(s):

Phase Transition ◽

Phase Transitions ◽

Potential Barrier ◽

Direct Contact ◽

First Order ◽

First Order Phase Transition ◽

Current Voltage ◽

Current Voltage Characteristics ◽

First Order Phase ◽

Metal Polymer

The article is devoted to the study of influence of the first-order phase transition in a metal (In) on changes in the metal/polymer potential barrier. The metal that undergoes the phase transition is not in direct contact with the polymer film. Analysis of the current-voltage characteristics allows to calculate the changes in the magnitude of the metal/polymer potential barrier at the phase transitions in In.

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