scholarly journals The intricate lattice dynamics of perovskite oxides

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
A. Bussmann-Holder ◽  
J.H. Ko ◽  
K. Roleder
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Lattice Dynamics ◽  
Finite Size ◽  
Perovskite Oxides ◽  
Formation Temperature ◽  
Phonon Modes ◽  
Nonlinear Approach ◽  
Local Lattice ◽  
Local Anomalies

The lattice dynamics of perovskite oxides are investigated theoretically within the polarizability model which is a nonlinear approach taking into account anharmonic electron-lattice interactions. The emphasis is on local lattice anomalies which appear in the phonon modes dispersion. Above the actual phase transition temperature finite size polarized clusters appear at an onset temperature TBH which marks the precursor formation temperature. These local anomalies appear as well experimentally and are reviewed for various perovskite compounds.

A First-Principles Study of Electron-Phonon Coupling of OsB2

2014 ◽  
Vol 597 ◽  
pp. 113-116
Author(s):  
Yue Qin Wang ◽  
Juan Gao ◽  
Shao Ping Yan
Keyword(s):  
Transition Temperature ◽  
First Principles ◽  
Linear Response ◽  
Lattice Dynamics ◽  
Superhard Material ◽  
Superconducting Transition ◽  
Phonon Coupling ◽  
Phonon Modes ◽  
Electron Phonon Coupling ◽  
Coulomb Pseudopotential

We investigated the lattice dynamics and electron-phonon coupling (EPC) of superhard material OsB2by first-principles linear response calculations. The calculated EPC parameters for the optical phonon modes at Г indicate that the heavy Os atoms play the most important role in deciding the superconducting behavior, and there are sizeable contributions from lighter B atoms to EPC. Our calculated EPC constant is 0.42, and the estimated superconducting transition temperatureTcis 2.1 K using the Coulomb pseudopotentialμ*=0.125, in excellent agreement with the experimental ones.

The Finite Size Effect on The Metal-Insulator Transition of VO2 Films Grown by MOCVD

1991 ◽  
Vol 237 ◽  
Author(s):  
Hyung Kook Kim ◽  
R. P. Chiarello ◽  
Hoydoo You ◽  
M. H. L. Chang ◽  
T. J. Zhang ◽  
...  
Keyword(s):  
Phase Transition ◽  
Particle Size ◽  
Transition Temperature ◽  
Size Effect ◽  
Thermal Hysteresis ◽  
Finite Size ◽  
Finite Size Effect ◽  
Transition Width ◽  
Metal Insulator ◽  
Out Of Plane

ABSTRACTWe studied the finite size effect on the metal-insulator phase transition and the accompanying tetragonal to monoclinic structural phase transition of VO2 films grown by MOCVD. X-ray diffraction measurements and electrical conductivity measurements were done as a function of temperature for VO2 films with out-of plane particle size ranging from 60–310Å. Each VO2 film was grown on a thin TiO2 buffer layer, which in turn was grown by MOCVD on a polished sapphire (1120) substrate. The transition was found to be first order. As the out-of plane particle size becomes larger, the transition temperature shifts and the transition width narrows. For the 60Å film the transition was observed at ∼61°C with a transition width of ∼10°C, while for the 310Å film the transition temperature was ∼59°C and the transition width ∼2°C. We also observed thermal hysteresis for each film, which became smaller with increasing particle size.

SPIN FLUCTUATION EFFECTS IN SUPERCONDUCTING MAGNETIC ALLOYS

2004 ◽  
Vol 18 (12) ◽  
pp. 1795-1804
Author(s):  
A. K. MONDAL ◽  
S. K. ROY
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Theoretical Model ◽  
Impurity Concentration ◽  
Spin Fluctuation ◽  
Spin Fluctuations ◽  
Phonon Modes ◽  
Magnetic Alloys ◽  
Fluctuation Effects ◽  
Superconducting Parameters

A theoretical model for finite impurity concentration is proposed to evaluate the superconducting parameters of three binary alloys Ni – Zr , Co – Zr and Fe – Zr . The influence of spin fluctuations on the electron–phonon parameter and transition temperature are also evaluated for these alloys within the Zr -concentration range 0.50<x<0.70. The results obtained using a modified form of McMillan equation and local phonon modes lead to a closer agreement between the experimental and theoretical values indicating a possibility of phase transition.

Lattice dynamics and Raman spectrum of rutile TiO2: The role of soft phonon modes in pressure induced phase transition

2012 ◽  
Vol 137 (1) ◽  
pp. 282-289 ◽  
Author(s):  
Igor Lukačević ◽  
Sanjeev K. Gupta ◽  
Prafulla K. Jha ◽  
Davor Kirin
Keyword(s):  
Phase Transition ◽  
Raman Spectrum ◽  
Lattice Dynamics ◽  
Phonon Modes ◽  
Rutile Tio2

scholarly journals Особенности динамики решетки ферровольфрамат стронция в диапазоне температур 300-700 K

2020 ◽  
Vol 62 (12) ◽  
pp. 2169
Author(s):  
А.С. Анохин ◽  
А.Г. Разумная ◽  
А.В. Павленко
Keyword(s):  
Phase Transition ◽  
Raman Spectroscopy ◽  
Lattice Dynamics ◽  
Diffuse Phase Transition ◽  
Tetragonal Symmetry ◽  
Cubic Phase ◽  
Phonon Modes ◽  
Temperature Behaviour ◽  
Spectra Analysis ◽  
Diffuse Phase

The lattice dynamics of strontium ferrotungsten ceramics have been studied by Raman spectroscopy in the temperature range 300−700 K. The spectra analysis confirmed tetragonal symmetry of strontium ferrotungsten which is consistent with the XRD results. The features of the temperature behaviour of the phonon modes of strontium ferrotungsten are revealed, and it is shown that a diffuse phase transition from the tetragonal to the cubic phase occurs at temperatures of 410–500 K.

The structure of membranes and membrane proteins embedded in amorphous ice

1992 ◽  
Vol 50 (1) ◽  
pp. 432-433
Author(s):  
Uwe Lücken ◽  
Joachim Jäger
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Membrane Proteins ◽  
Phase Transition Temperature ◽  
Lipid Vesicles ◽  
Freezing Stress ◽  
Amorphous Ice ◽  
Different Temperatures ◽  
Band Pass ◽  
Lipid Polymorphism

TEM imaging of frozen-hydrated lipid vesicles has been done by several groups Thermotrophic and lyotrophic polymorphism has been reported. By using image processing, computer simulation and tilt experiments, we tried to learn about the influence of freezing-stress and defocus artifacts on the lipid polymorphism and fine structure of the bilayer profile. We show integrated membrane proteins do modulate the bilayer structure and the morphology of the vesicles.Phase transitions of DMPC vesicles were visualized after freezing under equilibrium conditions at different temperatures in a controlled-environment vitrification system. Below the main phase transition temperature of 24°C (Fig. 1), vesicles show a facetted appearance due to the quasicrystalline areas. A gradual increase in temperature leads to melting processes with different morphology in the bilayer profile. Far above the phase transition temperature the bilayer profile is still present. In the band-pass-filtered images (Fig. 2) no significant change in the width of the bilayer profile is visible.

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