Lattice dynamics of heavy rare-gas solids

1969 ◽  
Vol 47 (6) ◽  
pp. 617-625 ◽  
Author(s):  
N. P. Gupta ◽  
R. K. Gupta
Keyword(s):  
Iterative Method ◽  
Specific Heat ◽  
Lattice Dynamics ◽  
Reasonable Agreement ◽  
Zero Point ◽  
Central Force ◽  
Experimental Results ◽  
Rare Gas ◽  
Buckingham Potential ◽  
Phonon Spectra

Phonon spectra, dispersion curves, and the specific heat of frozen argon, krypton, and xenon have been studied using a quasiharmonic central force rigid-atom model with interactions up to eighth neighbors. The effect of zero-point vibration is included by an iterative method and a modified Buckingham potential is used. There is reasonable agreement between theoretical and experimental results. A number of possibilities for the improvement of results have been discussed.

Lattice dynamics of rare-gas solids by Kihara's potential: I. Phonon spectra

1975 ◽  
Vol 68 (1) ◽  
pp. 307-317 ◽  
Author(s):  
T. N. Agrawal ◽  
R. K. Gupta ◽  
G. L. Gupta
Keyword(s):  
Lattice Dynamics ◽  
Rare Gas ◽  
Phonon Spectra

Anharmonic Phonons in B.C.C. 4He

1972 ◽  
Vol 50 (11) ◽  
pp. 1152-1155 ◽  
Author(s):  
H. R. Glyde ◽  
F. C. Khanna
Keyword(s):  
Lattice Dynamics ◽  
Reasonable Agreement ◽  
Phonon Frequency ◽  
Frequency Dispersion ◽  
Dispersion Curves ◽  
Experimental Results ◽  
Matrix Approach ◽  
T Matrix

A T-matrix approach is used to calculate lattice dynamics of b.c.c. 4He. The phonon frequency dispersion curves and phonon group widths are in reasonable agreement with the experimental results of Osgood et al.

Effect of polarizability on the vibrational and thermal properties of rare gas solids

1978 ◽  
Vol 56 (7) ◽  
pp. 849-858 ◽  
Author(s):  
S. K. Jain ◽  
G. P. Srivastava
Keyword(s):  
Lattice Dynamics ◽  
Interatomic Potential ◽  
Phonon Dispersion ◽  
Zero Point ◽  
Rare Gas ◽  
Model Parameters ◽  
Point Energy ◽  
Phonon Dispersion Curves ◽  
Boundary Frequency ◽  
Experimental Values

A simple shell model theory has been developed for the study of lattice dynamics of monatomic crystals. The phonon dispersion curves and variations of heat capacities with temperature are reported for solidified krypton and argon. The model parameters have been evaluated using the recent experimental values of elastic constants, polarizability of atoms, and a zone boundary frequency in each case. The zero point effects are also included by expressing the zero point energy in terms of the interatomic potential. The agreement between the theoretical and experimental results is found to improve appreciably by incorporating polarizability of atoms.

SPECIFIC HEATS AND DISPERSION CURVES FOR CsCl ON THE BASIS OF THE SHELL MODEL

1967 ◽  
Vol 45 (10) ◽  
pp. 3339-3346 ◽  
Author(s):  
G. P. Srivastava ◽  
B. Dayal
Keyword(s):  
Specific Heat ◽  
Shell Model ◽  
Lattice Dynamics ◽  
Cesium Chloride ◽  
Dispersion Curves ◽  
Experimental Results ◽  
Fair Agreement ◽  
Chloride Crystal ◽  
Specific Heats ◽  
Positive Ions

The shell model of Dick and Overhauser as developed by Cochran and Woods el al. has been applied to study theoretically the lattice dynamics of a cesium chloride crystal. The polarizabilities of both negative and positive ions have been taken into account in this treatment. The charges on the shells of the two ions come out to be of different magnitude. It is seen that the theoretical specific-heat variation with temperature based on this model is in fair agreement with experimental results in the range for which they have been obtained. The theoretical dispersion curves in the three symmetry directions are also given.

Experimental Study on the Specific Heat Capacity Measurement of Water-Based Al2O3-Cu Hybrid Nanofluid by using Differential Thermal Analysis Method

2019 ◽  
Vol 15 ◽  
Author(s):  
Andaç Batur Çolak ◽  
Oğuzhan Yıldız ◽  
Mustafa Bayrak ◽  
Ali Celen ◽  
Ahmet Selim Dalkılıç ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Thermophysical Properties ◽  
Volume Concentration ◽  
Pure Water ◽  
Heat Capacity Measurement ◽  
Experimental Results ◽  
Hybrid Nanofluid ◽  
Capacity Measurement

Background: Researchers working in the field of nanofluid have done many studies on the thermophysical properties of nanofluids. Among these studies, the number of studies on specific heat are rather limited. In the study of the heat transfer performance of nanofluids, it is necessary to increase the number of specific heat studies, whose subject is one of the important thermophysical properties. Objective: The authors aimed to measure the specific heat values of Al2O3/water, Cu/water nanofluids and Al2O3-Cu/water hybrid nanofluids using the DTA method, and compare the results with those frequently used in the literature. In addition, this study focuses on the effect of temperature and volume concentration on specific heat. Method: The two-step method was used in the preparation of nanofluids. The pure water selected as the base fluid was mixed with the Al2O3 and Cu nanoparticles and Arabic Gum as the surfactant, firstly mixed in the magnetic stirrer for half an hour. It was then homogenized for 6 hours in the ultrasonic homogenizer. Results: After the experiments, the specific heat of nanofluids and hybrid nanofluid were compared and the temperature and volume concentration of specific heat were investigated. Then, the experimental results obtained for all three fluids were compared with the two frequently used correlations in the literature. Conclusion: Specific heat capacity increased with increasing temperature, and decreased with increasing volume concentration for three tested nanofluids. Cu/water has the lowest specific heat capacity among all tested fluids. Experimental specific heat capacity measurement results are compared by using the models developed by Pak and Cho and Xuan and Roetzel. According to experimental results, these correlations can predict experimental results within the range of ±1%.

LATTICE DYNAMICS OF THE BINARY APERIODIC CHAINS OF ATOMS I: FRACTAL DIMENSION OF PHONON SPECTRA

1995 ◽  
Vol 09 (12) ◽  
pp. 1429-1451 ◽  
Author(s):  
WŁODZIMIERZ SALEJDA
Keyword(s):  
Fractal Dimension ◽  
Lattice Dynamics ◽  
Nearest Neighbor ◽  
Average Distance ◽  
Local Maximum ◽  
Fractal Dimensions ◽  
Dimension Formula ◽  
Phonon Spectra ◽  
Wide Range ◽  
Silver Mean

The microscopic harmonic model of lattice dynamics of the binary chains of atoms is formulated and studied numerically. The dependence of spring constants of the nearest-neighbor (NN) interactions on the average distance between atoms are taken into account. The covering fractal dimensions [Formula: see text] of the Cantor-set-like phonon spec-tra (PS) of generalized Fibonacci and non-Fibonaccian aperiodic chains containing of 16384≤N≤33461 atoms are determined numerically. The dependence of [Formula: see text] on the strength Q of NN interactions and on R=mH/mL, where mH and mL denotes the mass of heavy and light atoms, respectively, are calculated for a wide range of Q and R. In particular we found: (1) The fractal dimension [Formula: see text] of the PS for the so-called goldenmean, silver-mean, bronze-mean, dodecagonal and Severin chain shows a local maximum at increasing magnitude of Q and R>1; (2) At sufficiently large Q we observe power-like diminishing of [Formula: see text] i.e. [Formula: see text], where α=−0.14±0.02 and α=−0.10±0.02 for the above specified chains and so-called octagonal, copper-mean, nickel-mean, Thue-Morse, Rudin-Shapiro chain, respectively.

Unbalance Response of a Dual Rotor System: Theory and Experiment

1993 ◽  
Vol 115 (4) ◽  
pp. 427-435 ◽  
Author(s):  
K. Gupta ◽  
K. D. Gupta ◽  
K. Athre
Keyword(s):  
System Theory ◽  
Transfer Matrix ◽  
Mode Shape ◽  
Reasonable Agreement ◽  
Complex Variables ◽  
Rotor System ◽  
Experimental Results ◽  
Unbalance Response ◽  
Theoretical Results ◽  
Theory And Experiment

A dual rotor rig is developed and is briefly discussed. The rig is capable of simulating dynamically the two spool aeroengine, though it does not physically resemble the actual aeroengine configuration. Critical speeds, mode shape, and unbalance response are determined experimentally. An extended transfer matrix procedure in complex variables is developed for obtaining unbalance response of dual rotor system. Experimental results obtained are compared with theoretical results and are found to be in reasonable agreement.

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