scholarly journals 127I NQR and Crystal Structure Studies of [N(CH3)4]2 CdI4

2000 ◽  
Vol 55 (1-2) ◽  
pp. 225-229 ◽  
Author(s):  
Hideta Ishihara ◽  
Keizo Horiuchi ◽  
Thorsten M. Gesing ◽  
Shi-qi Dou ◽  
J.-Christian Buhl ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Order Phase Transition ◽  
Intensity Ratio ◽  
Room Temperature ◽  
Liquid Nitrogen Temperature ◽  
Temperature Phase ◽  
First Order ◽  
First Order Phase Transition ◽  
First Order Phase

The temperature dependence of 127I NQR and DSC as well as the crystal structure at room temperature of the title compound were determined. This compound shows a first-order phase transition of an order-disorder type at 245 K. Eight 127I(v1:m = ±1/2 ↔ ±3/2) NQR lines of 79.57, 81.86, 82.56, 83.36, 84.68, 87.72, 88.34, and 88.86 MHz, and corresponding eight 127I(v2: m = ±3/2 ↔±5/2) NQR lines were observed at liquid nitrogen temperature. Three 127I(υi) NQR lines wfth an intensity ratio of 1:1:2 in the order of decreasing frequency were observed just above the transition point and two NQR lines except for the middle-frequency line disappeared around room temperature. This temperature behavior of NQR lines is very similar to that observed in [N(CH3)4]2Hgl4. Another first-order phase transition takes place at 527 K. The structure of the room-temperature phase was redetermined: orthorhombic, Pnma, Z = 4, a = 1342.8(3), b = 975.7(2), c = 1696.5(3) pm. The NQR result of three lines with an intensity ratio of 1:1:2 is in agreement with this structure. The thermal displacement parameters of atoms in both cations and anions are large.

scholarly journals N-Methylpyrrolidinium hydrogen tartrate (NMPHT): an above-room-temperature order–disorder molecular switchable dielectric material

RSC Advances ◽  
2017 ◽  
Vol 7 (39) ◽  
pp. 24368-24373 ◽  
Author(s):  
Aurang Zeb ◽  
Tariq Khan ◽  
Muhammad Adnan Asghar ◽  
Zhihua Sun ◽  
Zhenyue Wu ◽  
...  
Keyword(s):  
Phase Transition ◽  
Order Phase Transition ◽  
Room Temperature ◽  
Dielectric Material ◽  
First Order ◽  
First Order Phase Transition ◽  
First Order Phase

A new above-room-temperature molecular switchable dielectric material, which undergoes a first-order phase transition induced by the order-disorder transformation of cation, has been reported.

Room-Temperature First-Order Phase Transition in a Charge-Disproportionated Molecular Conductor (MeEDO-TTF)2PF6

2008 ◽  
Vol 20 (24) ◽  
pp. 7551-7562 ◽  
Author(s):  
Xiangfeng Shao ◽  
Yoshiaki Nakano ◽  
Masafumi Sakata ◽  
Hideki Yamochi ◽  
Yukihiro Yoshida ◽  
...  
Keyword(s):  
Phase Transition ◽  
Order Phase Transition ◽  
Room Temperature ◽  
First Order ◽  
Molecular Conductor ◽  
First Order Phase Transition ◽  
A Charge ◽  
First Order Phase

High Temperature Phase Transitions in BiFeO3

2009 ◽  
Vol 1199 ◽  
Author(s):  
Donna Arnold ◽  
Christopher M Kavanagh ◽  
Philip Lightfoot ◽  
Finlay Doogan Morrison
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Order Phase Transition ◽  
Structure Type ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
First Order ◽  
Β Phase ◽  
First Order Phase Transition ◽  
First Order Phase

AbstractThe high temperature phases of BiFeO3 have courted much controversy with many conflicting structural models reported, in particular for the paraelectric β-phase. High temperature powder neutron diffraction (PND) experiments indicate that the ferroelectric (R3c) α-phase transforms to the paraelectric β-phase at approximately 820 °C via a first order phase transition. We demonstrate that this phase is unambiguously orthorhombic, adopting the GdFeO3 structure-type with a space group Pbnm. On further heating BiFeO3 undergoes another first order phase transition (β-γ) at approximately 930 °C which is marked by a discontinuous decrease in cell volume consistent with an insulator-metal transition. Close inspection of the PND data show no evidence of any symmetry change, with the postulated γ-phase remaining orthorhombic Pbnm. In addition we present PND and impedance spectroscopy data for BiFeO3 which suggest that the so-called ‘Połomska’ transition observed by some authors at approximately 185 °C is not intrinsic.

Synthesis and Lattice Distortion of Ferroelectric/Antiferroelectric Bi(III)-containing Perovskites

2002 ◽  
Vol 755 ◽  
Author(s):  
Yoshiyuki Inaguma ◽  
Atsushi Miyaguchi ◽  
Tetsuhiro Katsumata
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Order Phase Transition ◽  
Lattice Distortion ◽  
High Temperature Phase ◽  
Temperature Phase ◽  
First Order ◽  
First Order Phase Transition ◽  
Lattice Distortions ◽  
First Order Phase

ABSTRACTBi(III)-containing perovskites Bi1/2Ag1/2TiO3 and Bi(M1/2Ti1/2)O3 (M= Co, Mg, and Ni) were synthesized under oxygen pressure as high as approximately 1 MPa and under a pressure as high as 6 GPa, and the lattice distortions were investigated. It was found that ferroelectric Bi1/2Ag1/2TiO3 may be rhombohedrally distorted. In constrast, Bi(M1/2Ti1/2)O3 (M= Co, Mg, and Ni), the structure of which is different from GdFeO3-type compound, is monoclinically distorted. The ratio of lattice parameters of the monoclinic perovskite-subcell for Bi(M1/2Ti1/2)O3 (M= Co, Mg, and Ni), am/bm is larger than that of GdFeO3-type perovskites, though the tolerance factor is close. In addition, it was found that Bi(Ni1/2Ti1/2)O3 undergoes a first-order phase transition from a GdFeO3-type phase(high-temperature phase) at around 490 K. These results indicate that the Bi3+ character in Bi(III)-containing perovskites strongly influences the structure distortion.

In Situ Measurement of Phase Transition of Layered Perovskite BaLn2Mn2O7

2010 ◽  
Vol 67 ◽  
pp. 113-117 ◽  
Author(s):  
Hiromi Nakano ◽  
Nobuo Ishizawa ◽  
Hirohisa Sato ◽  
Naoki Kamegashira
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Order Phase Transition ◽  
High Temperature Phase ◽  
Layered Perovskite ◽  
Temperature Phase ◽  
First Order ◽  
First Order Phase Transition ◽  
First Order Phase

The BaLn2Mn2O7 (Ln = rare earth) has a Sr3Ti2O7-type structure with double block oxygen octahedra belonging to the Ruddlesden-Popper-Type homologous series AO(ABO3)2. In-situ measurement of the phase transition for BaLn2Mn2O7 was performed using single-crystal X-ray diffraction and a high-temperature transmission electron microscope (TEM). Two types of transitions were observed in BaPr2Mn2O7: the transition from primitive tetragonal (P42/mnm) to body-centered tetragonal (I4/mmm) at around 400 K and the first-order phase transition at around 1040 K. Multiple phase transitions were also observed in BaEu2Mn2O7, with one from P42/mnm to I4/mmm at around 400 K and another, above 550 K, as a first-order phase transition. The high-temperature phase had a 1.5% lattice mismatch along the c-axis compared with the low-temperature phase. We succeeded in recording for the first time in-situ structural change in BaGd2Mn2O7 as a movie by high-temperature TEM. The high-temperature phase nucleated parallel to the (00l) plane as a layer above 550 K and grew until covering the entire inspected region at around 1023 K. The first-order phase transition was caused by the structural and/or electrical distortion of the layered perovskite structure composed of Jahn-Teller ion Mn3+.

35Cl NQR Spectra of Substituted N-(Phenyl)-2,2,2-Trichloroacetamides

1999 ◽  
Vol 54 (3-4) ◽  
pp. 261-269 ◽  
Author(s):  
B. Thimme Gowda ◽  
D. Krishna Bhat ◽  
Hartmut Fuess ◽  
Alarich Weiss
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Order Phase Transition ◽  
Phenyl Ring ◽  
First Order ◽  
First Order Phase Transition ◽  
35Cl Nqr ◽  
The Mean ◽  
First Order Phase ◽  
35Cl Nqr Spectra

Several substituted acetamides, XyC6H5_ y NHCOCCl3 (X=CH3 , NO2 , or Br and y= 1 or 2) have been synthesized and studied by NQR. The effect of ring substitution on the average υ(35Cl) NQR of the trichloroacetyl group is not substantial, but it affects the crystal structure of the substituted com-pounds. The NQR spectra of XyC6H5-y NHCOCCl 3 (where Xy =4-CH3 , 4-NO2 , and 2,3-(CH3)2) show six 35Cl NQR frequencies, each indicating the presence of two molecules in their respective asym-metric units. The temperature dependence of υ(35Cl) NQR of N-(4-methylphenyl)-2,2,2-trichloroacet-amide reveals that it undergoes a first order phase transition around 205 K. Its spectrum shows six lines up to 205 K and three lines thereafter. The latter triplet part of the spectrum fades out around 250 K due to librational motions in the crystal lattice, as the torsional motions of the CCl3 group are easily excit-ed. The 35Cl NQR spectra of all the methylsubstituted amides have been compared with those of the corresponding chlorosubstituted compounds. Generally there is no systematic variation of the mean val-ues of υ(35Cl) NQR or the trichloroacetyl group with the substituents in the phenyl ring. The ω C-Cl frequencies of the trichloroacetyl group of all the v-substituted N-(phenyl)-2,2,2-trichloroacetamides have been estimated using NQR substituent parameters (k) and the frequencies of N-(phenyl)-2,2,2-tri-chloroacetamide. Agreement between these values and the experimental frequencies is quite good. The υ(35Cl) NQR of these amides has also been correlated with Σki of the substituents. Further υ(35Cl) NQR spectra of mono-and trichloroacetamides have been correlated.

scholarly journals Gravitational wave signals of dark matter freeze-out

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Danny Marfatia ◽  
Po-Yan Tseng
Keyword(s):  
Phase Transition ◽  
Dark Matter ◽  
Gravitational Waves ◽  
Order Phase Transition ◽  
First Order ◽  
Stochastic Background ◽  
First Order Phase Transition ◽  
Relic Abundance ◽  
First Order Phase ◽  
Freeze Out

Abstract We study the stochastic background of gravitational waves which accompany the sudden freeze-out of dark matter triggered by a cosmological first order phase transition that endows dark matter with mass. We consider models that produce the measured dark matter relic abundance via (1) bubble filtering, and (2) inflation and reheating, and show that gravitational waves from these mechanisms are detectable at future interferometers.

Discovering a First-Order Phase Transition in the Li–CeO2 System

Nano Letters ◽  
2017 ◽  
Vol 17 (2) ◽  
pp. 1282-1288 ◽  
Author(s):  
Kaikai Li ◽  
Xiaoye Zhou ◽  
Anmin Nie ◽  
Sheng Sun ◽  
Yan-Bing He ◽  
...  
Keyword(s):  
Phase Transition ◽  
Order Phase Transition ◽  
First Order ◽  
First Order Phase Transition ◽  
First Order Phase
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