scholarly journals INTERATOMIC INTERACTIONS AND ZONE CENTRE PHONONS IN MULTIFERROIC BiFeO3 CERAMICS

2013 ◽  
Vol 22 ◽  
pp. 134-139 ◽  
Author(s):  
M. M. SINHA ◽  
RUBY ◽  
H. C. GUPTA
Keyword(s):  
Force Constant ◽  
Ferroelectric Properties ◽  
Compressive Strain ◽  
Potential Energy Distribution ◽  
Bending Force ◽  
Short Range Force ◽  
Multiferroic Bifeo3 ◽  
Zone Centre ◽  
Range Force ◽  
Good Agreement

The existence of an epitaxially stabilized tetragonal-like (“T -like”) monoclinic phase in BiFeO 3 thin films with high levels of compressive strain has been reported recently. While their structural and ferroelectric properties are different from those of rhombohedral-like (“R-like”) films with lower levels of strain, little information exists on magnetic properties. In this study we have applied a short range force constant model by using normal coordinates to investigate the Raman and the infrared wavenumbers in tetragonal BiFeO 3 having space group P4mm (C4v1). The calculation of zone center phonons has been made by using three stretching and six bending force constants. The calculated Raman and infrared wavenumbers are in very good agreement with the observed ones. The potential energy distribution has also been investigated for determining the significance of contribution from each force constant toward the Raman and the infrared wavenumbers.

LATTICE DYNAMICAL INVESTIGATIONS FOR RAMAN AND THE INFRARED FREQUENCIES OF Cs2HgCl4

2013 ◽  
Vol 22 ◽  
pp. 694-700 ◽  
Author(s):  
SHAVEEN GARG ◽  
M. M. SINHA ◽  
H. C. GUPTA
Keyword(s):  
Force Constant ◽  
Orthorhombic Phase ◽  
Potential Energy Distribution ◽  
Short Range Force ◽  
Wave Numbers ◽  
Zone Centre ◽  
Infrared Frequencies ◽  
Infrared Wave ◽  
Range Force ◽  
Good Agreement

A short-range force constant model has been applied in investigating the Raman and infrared modes in insulating Cs2HgCl4 in orthorhombic phase having space group Pnam using normal coordinate analysis. Calculations on zone centre phonons have been made with twelve stretching and three bending force constants. The calculated Raman and infrared wave numbers are in good agreement with the available experimental results. The potential energy distribution has also been investigated for determining the significance of contribution from each force constant towards the Raman and the infrared wave numbers.

Lattice Vibrations of the Cooperites PdO and PtS

1989 ◽  
Vol 44 (3) ◽  
pp. 169-172 ◽  
Author(s):  
G. Kliche
Keyword(s):  
Force Field ◽  
Vibrational Spectra ◽  
Short Range ◽  
Lattice Vibration ◽  
Covalent Bonding ◽  
Lattice Vibrations ◽  
Vibration Frequencies ◽  
Short Range Force ◽  
Range Force ◽  
Good Agreement

The vibrational spectra of the cooperite type compounds PdO and PtS (space group P42/mmc - D4h9, Z = 2) are analyzed. Good agreement between experimental and calculated lattice vibration frequencies is obtained using a force field which includes short-range force constants only. This demonstrates a highly covalent bonding character of the cooperites.

Comparison of ring bending strain with infrared bending vibrations

1969 ◽  
Vol 22 (12) ◽  
pp. 2575
Author(s):  
IJ Miller
Keyword(s):  
Force Constant ◽  
Empirical Formula ◽  
Reasonable Agreement ◽  
Bending Vibrations ◽  
Bending Force ◽  
Bending Strain ◽  
Pendulum Dynamics ◽  
Good Agreement

An empirical formula which has been shown to give good values for ring bending strain in small rings has been applied to infrared bending vibrations. The derived dynamics are of a ?pendulum? character, and reasonable agreement is obtained in calculating the C-C-C bending force constant from the empirical formula constant. Resultant anharmonicities are calculated from the ?pendulum? dynamics, and good agreement is obtained with experimentally determined levels up to the 060 level of CO2 and 040 for HCN.

Rigid-Ion-Model Treatment of the Vibrational Spectra of Calcium and Strontium Chloride Hexahydrate Crystals

1988 ◽  
Vol 42 (1) ◽  
pp. 60-64 ◽  
Author(s):  
W. Kevin Winnett ◽  
Charles P. Nash
Keyword(s):  
Force Constants ◽  
Water Molecules ◽  
Strontium Chloride ◽  
Bending Force ◽  
Short Range Force ◽  
Partial Charges ◽  
Chloride Hexahydrate ◽  
Model Treatment ◽  
Range Force ◽  
Rigid Ion Model

Single-crystal Raman spectra at 77 K in the 80–3500 cm−1 range are reported for CaCl2 · 6H2O(D2O) and SrCl2 · 6H2O(D2O). Excellent fits to the experimental spectra were obtained with the use of a thirteen-parameter force field based on the rigid-ion model supplemented with stretching and bending force constants for the water molecules and selected short-range force constants in the Bravais cell. The libration frequencies of both the bridging (four-coordinate) and the terminal (three-coordinate) water molecules were found to depend almost exclusively on their partial charges.

scholarly journals Constitutive Modeling of the Densification Behavior in Open-Porous Cellular Solids

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2731
Author(s):  
Ameya Rege
Keyword(s):  
Constitutive Model ◽  
Cell Walls ◽  
Compressive Strain ◽  
Pore Collapse ◽  
Compressive Response ◽  
Linear Elastic ◽  
Nonlinear Springs ◽  
Different Types ◽  
Point Of Intersection ◽  
Good Agreement

The macroscopic mechanical behavior of open-porous cellular materials is dictated by the geometric and material properties of their microscopic cell walls. The overall compressive response of such materials is divided into three regimes, namely, the linear elastic, plateau and densification. In this paper, a constitutive model is presented, which captures not only the linear elastic regime and the subsequent pore-collapse, but is also shown to be capable of capturing the hardening upon the densification of the network. Here, the network is considered to be made up of idealized square-shaped cells, whose cell walls undergo bending and buckling under compression. Depending on the choice of damage criterion, viz. elastic buckling or irreversible bending, the cell walls collapse. These collapsed cells are then assumed to behave as nonlinear springs, acting as a foundation to the elastic network of active open cells. To this end, the network is decomposed into an active network and a collapsed one. The compressive strain at the onset of densification is then shown to be quantified by the point of intersection of the two network stress-strain curves. A parameter sensitivity analysis is presented to demonstrate the range of different material characteristics that the model is capable of capturing. The proposed constitutive model is further validated against two different types of nanoporous materials and shows good agreement.

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