Second order elastic anomalies in barium titanate from orthorhombic to rhombohedral phase transition

Pramana ◽  
1994 ◽  
Vol 43 (3) ◽  
pp. 181-187 ◽  
Author(s):  
B Subramanyam
Keyword(s):  
Phase Transition ◽  
Barium Titanate ◽  
Rhombohedral Phase ◽  
Second Order ◽  
Elastic Anomalies

First-Principles Study of Lattice Dynamics, Structural Phase Transition, and Thermodynamic Properties of Barium Titanate

2016 ◽  
Vol 71 (8) ◽  
pp. 759-768 ◽  
Author(s):  
Huai-Yong Zhang ◽  
Zhao-Yi Zeng ◽  
Ying-Qin Zhao ◽  
Qing Lu ◽  
Yan Cheng
Keyword(s):  
Phase Transition ◽  
Barium Titanate ◽  
Thermodynamic Properties ◽  
Structural Phase Transition ◽  
First Principles ◽  
Lattice Dynamics ◽  
Density Functional ◽  
Structural Phase ◽  
Rhombohedral Phase ◽  
Site Symmetry

AbstractLattice dynamics, structural phase transition, and the thermodynamic properties of barium titanate (BaTiO3) are investigated by using first-principles calculations within the density functional theory (DFT). It is found that the GGA-WC exchange-correlation functional can produce better results. The imaginary frequencies that indicate structural instability are observed for the cubic, tetragonal, and orthorhombic phases of BaTiO3 and no imaginary frequencies emerge in the rhombohedral phase. By examining the partial phonon density of states (PDOSs), we find that the main contribution to the imaginary frequencies is the distortions of the perovskite cage (Ti-O). On the basis of the site-symmetry consideration and group theory, we give the comparative phonon symmetry analysis in four phases, which is useful to analyze the role of different atomic displacements in the vibrational modes of different symmetry. The calculated optical phonon frequencies at Γ point for the four phases are in good agreement with other theoretical and experimental data. The pressure-induced phase transition of BaTiO3 among four phases and the thermodynamic properties of BaTiO3 in rhombohedral phase have been investigated within the quasi-harmonic approximation (QHA). The sequence of the pressure-induced phase transition is rhombohedral→orthorhombic→tetragonal→cubic, and the corresponding transition pressure is 5.17, 5.92, 6.65 GPa, respectively. At zero pressure, the thermal expansion coefficient αV, heat capacity CV, Grüneisen parameter γ, and bulk modulus B of the rhombohedral phase BaTiO3 are estimated from 0 K to 200 K.

Void pattern fluctuation in p-AgBr interactions at 400 GeV/c

2016 ◽  
pp. 4115-4125
Author(s):  
Argha Deb
Keyword(s):  
Experimental Data ◽  
Phase Transition ◽  
Phase Space ◽  
Second Order ◽  
Hadron Phase

The event-by-event fluctuation of hadronic patterns is investigated by finding a measure of the non-hadronic regions, the voids, for the experimental data of p-AgBr interactions at 400 GeV/c considering the anisotropy of phase space. Two moments of the event-to-event fluctuation of voids, <Gq> and Sq have been calculated as defined by R. C. Hwa and Q. H. Zhang to quantify the dependence of the voids on the bin sizes. The results suggest that no quark-hadron phase transition of second order have taken place for p-AgBr interactions at 400 GeV/c. The result have been compared with the result of VENUS generated data.

scholarly journals Elastic Properties and Energy Loss Related to the Disorder–Order Ferroelectric Transitions in Multiferroic Metal–Organic Frameworks [NH4][Mg(HCOO)3] and [(CH3)2NH2][Mg(HCOO)3]

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3125
Author(s):  
Zhiying Zhang ◽  
Hongliang Yu ◽  
Xin Shen ◽  
Lei Sun ◽  
Shumin Yue ◽  
...  
Keyword(s):  
Phase Transition ◽  
Energy Loss ◽  
Elastic Properties ◽  
Ferroelectric Phase ◽  
Loss Modulus ◽  
Structural Phase ◽  
Metal Organic Frameworks ◽  
First Order ◽  
Metal Organic ◽  
Elastic Anomalies

Elastic properties are important mechanical properties which are dependent on the structure, and the coupling of ferroelasticity with ferroelectricity and ferromagnetism is vital for the development of multiferroic metal–organic frameworks (MOFs). The elastic properties and energy loss related to the disorder–order ferroelectric transition in [NH4][Mg(HCOO)3] and [(CH3)2NH2][Mg(HCOO)3] were investigated using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). The DSC curves of [NH4][Mg(HCOO)3] and [(CH3)2NH2][Mg(HCOO)3] exhibited anomalies near 256 K and 264 K, respectively. The DMA results illustrated the minimum in the storage modulus and normalized storage modulus, and the maximum in the loss modulus, normalized loss modulus and loss factor near the ferroelectric transition temperatures of 256 K and 264 K, respectively. Much narrower peaks of loss modulus, normalized loss modulus and loss factor were observed in [(CH3)2NH2][Mg(HCOO)3] with the peak temperature independent of frequency, and the peak height was smaller at a higher frequency, indicating the features of first-order transition. Elastic anomalies and energy loss in [NH4][Mg(HCOO)3] near 256 K are due to the second-order paraelectric to ferroelectric phase transition triggered by the disorder–order transition of the ammonium cations and their displacement within the framework channels, accompanied by the structural phase transition from the non-polar hexagonal P6322 to polar hexagonal P63. Elastic anomalies and energy loss in [(CH3)2NH2][Mg(HCOO)3] near 264 K are due to the first-order paraelectric to ferroelectric phase transitions triggered by the disorder–order transitions of alkylammonium cations located in the framework cavities, accompanied by the structural phase transition from rhombohedral R3¯c to monoclinic Cc. The elastic anomalies in [NH4][Mg(HCOO)3] and [(CH3)2NH2][Mg(HCOO)3] showed strong coupling of ferroelasticity with ferroelectricity.

A crystallographic study of the second-order phase transition in bis(p-toluene sulphonate) diacetylene polymer crystals

1980 ◽  
Vol 69 ◽  
pp. 49 ◽  
Author(s):  
Richard L. Williams ◽  
David Bloor ◽  
David N. Batchelder ◽  
Michael B. Hursthouse ◽  
William B. Daniels
Keyword(s):  
Phase Transition ◽  
Order Phase Transition ◽  
Second Order ◽  
Polymer Crystals ◽  
Crystallographic Study ◽  
Second Order Phase Transition

Second-order phase transition of high isotactic polypropylene at high temperature

Polymer ◽  
2002 ◽  
Vol 43 (4) ◽  
pp. 1473-1481 ◽  
Author(s):  
Fangming Gu ◽  
Masamichi Hikosaka ◽  
Akihiko Toda ◽  
Swapan Kumar Ghosh ◽  
Shinichi Yamazaki ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Isotactic Polypropylene ◽  
Order Phase Transition ◽  
Second Order ◽  
Second Order Phase Transition

scholarly journals Entanglement in a second-order quantum phase transition

2004 ◽  
Vol 69 (2) ◽  
Author(s):  
Julien Vidal ◽  
Guillaume Palacios ◽  
Rémy Mosseri
Keyword(s):  
Phase Transition ◽  
Quantum Phase Transition ◽  
Second Order ◽  
Quantum Phase
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