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.

Molecular Motions and Phase Transitions in Solid CH3NH3PbX3 (X = C1, Br, I) as Studied by NMR and NQR

1991 ◽  
Vol 46 (3) ◽  
pp. 240-246 ◽  
Author(s):  
Qiang Xu ◽  
Taro Eguchi ◽  
Hirokazu Nakayama ◽  
Nobuo Nakamura ◽  
Michihiko Kishita
Keyword(s):  
Phase Transitions ◽  
Temperature Dependence ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Molecular Motions ◽  
Isotropic Reorientation ◽  
Higher Temperature ◽  
Successive Phase

AbstractThe temperature dependence of 35C1, 81Br, and 127I NQR frequencies and 1Hspin-lattice relaxation times (T1) for CH3NH3PbX3 (X = Cl, Br, I) was measured through the successive phase transitions in these solids. The isotropic reorientation of the CH3NH3 ions takes place in the higher-temperature phases (tetragonal [I4/mcm] and cubic) of the three salts (Ea= 11 kJ mol -1). T1's in the lowest-temperature phases (orthorhombic) indicate that the cations undergo correlated C3-reorientation in the chloride (Ea = 5.45 kJ mol -1)and in the iodide (Ea = 5.80 kJ mol -1, whereas correlated (Ea = 2.40 kJ mol-1) and uncorrected (Ea = 7.50 kJ mol-1) C3- reorientations are excited in the bromide. It is also revealed that the rotational tunneling of the cations governs T1 at lowtemperature region in the orthorhombic phases of these salts

Studies of Successive Phase Transitions and Molecular Motions in [Mg(H2O)6][SiF6] by 1,2H and 19F NMR

1998 ◽  
Vol 53 (6-7) ◽  
pp. 453-458 ◽  
Author(s):  
Junko Kimura ◽  
Takeshi Fukase ◽  
Motohiro Mizuno ◽  
Masahiko Suhara
Keyword(s):  
Phase Transitions ◽  
Nmr Spectra ◽  
Quadrupole Coupling Constant ◽  
Coupling Constant ◽  
Molecular Motions ◽  
Exponential Factor ◽  
H Nmr ◽  
Quadrupole Coupling ◽  
Constant E ◽  
Successive Phase

Abstract The successive phase transitions of [Mg(H2O)6][SiF6] were studied by measuring 2H NMR spectra. The quadrupole coupling constant e2Qq/h and asymmetry parameter η changed drastically at each transition temperature. 1,2H and 19F NMR Tl were measured for this compound to study the relation between the molecular motions and the successive phase transitions. The activation energy Ea and the pre-exponential factor τ0 for the reorientation of [SiF6]2- were estimated as 28 kJmol-1 and 6.0 x 10-14 s, and those of the 180° flip of H2O as 33 kJmol-1 and 4.0x 10-14 s. These two motions occur rapidly even in phase V. For the reorientation of [Mg(H2O)6]2+ , Ea = 62 kJmol-1 and τ0 = 1.1 x 10-16 s were obtained from the simulation of 2H NMR spectra. The jump rate of this motion is of the order of 104 -106 s-1 in phase II. These results suggest that the successive phase transitions are closely related to the motion of [Mg(H2O)6]2+ .

Electric and Magnetic Properties of Transition-Metal Carbide Sc3TC4 (T=Co, Ru, Os)

2016 ◽  
Vol 257 ◽  
pp. 34-37
Author(s):  
Takuto Kazama ◽  
Minoru Maeda ◽  
Kouichi Takase ◽  
Yoshiki Takano ◽  
Tadataka Watanabe
Keyword(s):  
Phase Transition ◽  
Magnetic Properties ◽  
Phase Transitions ◽  
Transition Metal ◽  
Density Wave ◽  
Transition Metal Carbide ◽  
Superconducting Transition ◽  
Metal Carbides ◽  
Low Dimensional ◽  
Successive Phase

We investigate electric and magnetic properties of quasi-one-dimensional transition-metal carbides Sc3TC4 (T = Co, Ru, and Os), and their mixed crystals Sc3(Co1-xRux)C4 and Sc3(Ru1-xOsx)C4. Sc3CoC4 exhibits successive phase transitions of charge-density-wave transition at TCDW ~ 140 K, Peierls-like structural transition at Ts ~ 70 K, and superconducting transition at Tc ~ 5 K. Sc3RuC4 and Sc3OsC4 exhibit a phase transition at T* ~ 220 K and 250 K, respectively, which should occur in the low-dimensional electronic structure. For Sc3CoC4, it is revealed by the investigation of the electric and magnetic properties of Sc3(Co1-xRux)C4 that the phase transitions at TCDW, Ts, and Tc exhibit different robustness against Ru doping. For Sc3RuC4 and Sc3OsC4, it is revealed by the investigation of the electric and magnetic properties of Sc3(Ru1-xOsx)C4 that an identical kind of phase transition occurs at T*. Additionally, the present study reveals that the phase transition at T* in Sc3RuC4 and Sc3OsC4 is inherently different from the phase transitions at TCDW, Ts, and Tc in Sc3CoC4.

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.

Dielectric, pyroelectric, piezoelectric and optical investigation of the phase transition sequence in BaZnGeO4

1994 ◽  
Vol 209 (2) ◽  
Author(s):  
S. Y. Huang ◽  
R. von der Mühll ◽  
J. Ravez ◽  
P. Hagenmuller
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Optical Investigation ◽  
Transition Sequence ◽  
Successive Phase

AbstractThe successive phase transitions of a BaZnGeO

Phase Transitions in 4,4´-Dichlorobenzophenone as Studied by 35Cl FT-NQR

1994 ◽  
Vol 49 (1-2) ◽  
pp. 267-272 ◽  
Author(s):  
Hirokazu Nakayama ◽  
Taro Eguchi ◽  
Nobuo Nakamura
Keyword(s):  
Phase Transition ◽  
Fourier Transform ◽  
Phase Transitions ◽  
Room Temperature ◽  
Thermal Hysteresis ◽  
Thermal Anomaly ◽  
Hysteresis Phenomenon ◽  
Transform Method ◽  
Three Phase ◽  
Successive Phase

Abstract The temperature dependence of 35Cl NQR frequencies in 4,4´-dichlorobenzophenone was measured between 9.3 and 372 K by the pulse Fourier-transform method. Successive phase transitions were observed at 189 and 194 K. Concerning these phase transitions, the curious thermal hysteresis phenomenon found in a previous NQR experiment was not reproduced in the present study. It also follow s that NQR indicates another phase transition around 220 K, although no thermal anomaly was detected there by DTA. Tentative explanations for these three phase transitions are presented in relation to the incommensurability between 189 and 220 K. In addition, a novel phase transition was found to occur at 331 K according to both DTA and 35Cl NQR. A single NQR line observed at room temperature splits into two components above 331 K, suggesting that the symmetry above 331 K is lower than that at room temperature. This is the behavior of re-entrant phase transition, and it reveals the quasi-continuous nature.

scholarly journals A Veritable Zoology of Successive Phase Transitions in the Asymmetric q-Voter Model on Multiplex Networks

Entropy ◽  
2020 ◽  
Vol 22 (9) ◽  
pp. 1018
Author(s):  
Anna Chmiel ◽  
Julian Sienkiewicz ◽  
Agata Fronczak ◽  
Piotr Fronczak
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Continuous Phase ◽  
Voter Model ◽  
Complete Graphs ◽  
Opinion Formation ◽  
Multiplex Networks ◽  
Multiplex Network ◽  
Two Parameters ◽  
Successive Phase

We analyze a nonlinear q-voter model with stochastic noise, interpreted in the social context as independence, on a duplex network. The size of the lobby q (i.e., the pressure group) is a crucial parameter that changes the behavior of the system. The q-voter model has been applied on multiplex networks, and it has been shown that the character of the phase transition depends on the number of levels in the multiplex network as well as on the value of q. The primary aim of this study is to examine phase transition character in the case when on each level of the network the lobby size is different, resulting in two parameters q1 and q2. In a system of a duplex clique (i.e., two fully overlapped complete graphs) we find evidence of successive phase transitions when a continuous phase transition is followed by a discontinuous one or two consecutive discontinuous phase transitions appear, depending on the parameter. When analyzing this system, we even encounter mixed-order (or hybrid) phase transition. The observation of successive phase transitions is a new quantity in binary state opinion formation models and we show that our analytical considerations are fully supported by Monte-Carlo simulations.

Successive phase transitions in the MeLiBO4type crystals

1985 ◽  
Vol 63 (1) ◽  
pp. 13-28 ◽  
Author(s):  
K. S. Aleksandrov ◽  
D. H. Blat ◽  
V. I. Zinenko ◽  
I. M. Iskornev ◽  
R. F. Klevtsova ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Successive Phase

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.

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