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1.
S. Yu. Davydov 《Physics of the Solid State》2010,52(4):810-812
The elastic properties of graphene have been described in terms of the Keating model. It has been shown that the two-dimensional
structure of graphene is described by two independent elastic constants, like an isotropic solid. The Young’s modulus and
the Poisson’s ratio have been determined. The results are compared with the experimental data obtained for graphite. 相似文献
2.
In the framework of the Keating model with allowance made for the anharmonic constant of the central interaction between the
nearest neighbors μ, analytical expressions have been obtained for three third-order independent elastic constants c
ijk
(μ, ζ) of single-layer graphene, where ζ = (2α − β)/(4α + β) is the Kleinman internal displacement parameter and α and β are
the harmonic constants of the central interaction between the nearest neighbors and the noncentral interaction between the
next-nearest neighbors, respectively. The dependences of the second-order elastic constants on the pressure p have been determined. It has been shown that the moduli c
11 and c
22 differently respond to the pressure. Therefore, graphene is isotropic in the harmonic approximation, whereas the inclusion
of anharmonicity leads to the appearance of the anisotropy. 相似文献
3.
xSb2O3-40TeO2-(60 − x)
V2O5 glasses with 0 ≤ x ≤ 10 (in mol%) have been
prepared by rapid- melt quenching method. DSC curves of these ternary glasses have been
investigated. The glass transition properties that have been measured and reported in this
paper, include the glass transition
temperature (T
g
), glass transition width
(ΔT
g
), heat capacity
change at glass transition
(ΔC
P
) and
fragility (F). Thermal stability, Poisson’s ratio, fragility and glass
forming tendency of these glasses have been estimated, to determine relationship between
chemical composition and the thermal stability or to interpret the structure of glass. In
addition, Makishima and Makenzie’s theory was applied for determination of Young’s
modulus, bulk modulus and shear modulus, indicating a strong relation between elastic
properties and structure of glass. Generally, results of this work show that glass with
x = 0 has the highest shear, bulk and Young’s moduli which make it as
suitable candidate for the manufacture of strong glass fibers in technological
applications; but it should be mentioned that glass with x = 8 has higher
handling temperature and super resistance against thermal attack. 相似文献
4.
B. K. Kardashev T. S. Orlova B. I. Smirnov T. E. Wilkes K. T. Faber 《Physics of the Solid State》2009,51(12):2463-2468
This paper reports on a study performed in the temperature range 100–293 K, in air and in vacuum, for the amplitude and time
dependences of the Young’s modulus and the internal friction (ultrasound damping) of biocarbon precursors prepared from white
pine wood at two pyrolysis (carbonization) temperatures of 1000 and 2400°C. The measurements have been conducted by the resonance
technique with a composite vibrator on samples cut along and across the tree growth direction. The desorption of molecules
of the external medium at low amplitudes of ultrasonic vibrations has been found to produce the pronounced influence on the
effective elastic modulus and elastic vibration decrement. The data obtained from acoustic measurements of the amplitude dependences
of the elastic modulus have been used to estimate the microplastic properties of the samples. It has been shown that increasing
the carbonization temperature gives rise to noticeable changes in the Young’s modulus and internal friction, as well as to
reduction of the microplastic stress σ
y
of the biomaterial studied. The stress σ
y
of the samples cut across the growth direction has been found to be substantially smaller than that of the “longitudinal”
samples. The elastic and microplastic properties of precursors prepared from white pine wood have been compared with those
of the white eucalyptus wood. 相似文献
5.
Ab initio calculations were performed to investigate electronic and elastic properties of the newly discovered 7.5 K superconductor:
layered Nb2InC. As a result, electronic bands, total and site-projected l—decomposed density of states at the Fermi level, shape of the Fermi surface for Nb2InC were obtained for the first time. Besides, independent elastic constants, bulk modulus, compressibility, shear modulus,
Young’s modulus, Poisson’s ratio together with the elastic anisotropy parameters and indicator of brittle/ductile behavior
of Nb2InC were evaluated and analyzed in comparison with the available data. 相似文献
6.
Yasemin ?. ?iftci Kemal ?olako?lu Cansu ?oban Engin Delig?z 《Central European Journal of Physics》2012,10(1):197-205
The structural, elastic and thermodynamic characteristics of CeGa2 compound in the AlB2 (space group: P6/mmm) and the omega trigonal (space group: P-3m1) type structures are investigated using the methods of density
functional theory within the generalized gradient approximation (GGA). The thermodynamic properties of the considered structures
are obtained through the quasi-harmonic Debye model. The results on the basic physical parameters, such as the lattice constant,
the bulk modulus, the pressure derivative of bulk modulus, the phase-transition pressure (P
t
) from P6/mmm to P-3m1 structure, the second-order elastic constants, Zener anisotropy factor, Poisson’s ratio, Young’s modulus,
and the isotropic shear modulus are presented. In order to gain further information, the pressure and temperature-dependent
behavior of the volume, the bulk modulus, the thermal expansion coefficient, the heat capacity, the entropy, Debye temperature
and Grüneisen parameter are also evaluated over a pressure range of 0–6 GPa and a wide temperature range of 0–1800 K. The
obtained results are in agreement with the available experimental and the other theoretical values. 相似文献
7.
Certain organic crystals are found to possess high non-linear optical coefficients, often one to two orders of magnitude higher
than those of the well-known inorganic non-linear optical materials. Benzoyl glycine is one such crystal whose optical second-harmonic
generation efficiency is much higher than that of potassium dihydrogen phosphate. Single crystals of benzoyl glycine are grown
by solvent evaporation technique usingN, N-dimethyl formamide as the solvent. All the nine second-order elastic stiffness constants of this orthorhombic crystal are
determined from ultrasonic wave velocity measurements employing the pulse echo overlap technique. The anisotropy of elastic
wave propagation in this crystal is demonstrated by plotting the phase velocity, slowness, Young’s modulus and linear compressibility
surfaces along symmetry planes. The volume compressibility, bulk modulus and relevant Poisson’s ratios are also determined.
Variation of the diagonal elastic stiffness constants with temperature over a limited range are measured and reported. 相似文献
8.
Seddik T. Khenata R. Merabiha O. Bouhemadou A. Bin-Omran S. Rached D. 《Applied Physics A: Materials Science & Processing》2012,106(3):645-653
The elastic, electronic and thermodynamic properties of fluoro-perovskite KZnF3 have been calculated using the full-potential linearized augmented plane wave (FP-LAPW) method. The exchange-correlation
potential is treated with the generalized gradient approximation of Perdew-Burke-Ernzerhof (GGA-PBE). Also, we have used the
Engel and Vosko GGA formalism (GGA-EV) to improve the electronic band structure calculations. The calculated structural properties
are in good agreement with available experimental and theoretical data. The elastic constants C
ij
are calculated using the total energy variation with strain technique. The shear modulus, Young’s modulus, Poisson’s ratio
and the Lamé coefficients for polycrystalline KZnF3 aggregates are estimated in the framework of the Voigt-Reuss-Hill approximations. The ductility behavior of this compound
is interpreted via the calculated elastic constants C
ij
. Electronic and bonding properties are discussed from the calculations of band structure, density of states and electron
charge density. The thermodynamic properties are predicted through the quasi-harmonic Debye model, in which the lattice vibrations
are taken into account. The variation of bulk modulus, lattice constant, heat capacities and the Debye temperature with pressure
and temperature are successfully obtained. 相似文献
9.
We have performed the first principles calculation by using the plane-wave pseudopotential approach with the generalized gradient approximation for investigating the structural, electronic, and elastic properties Na-As systems (NaAs in NaP, LiAs and AuCu-type structures, NaAs2 in MgCu2-type structure, Na3As in Na3As, Cu3P and Li3Bi-type structures, and Na5As4 in A5B4-type structure). The lattice parameters, cohesive energy, formation energy, bulk modulus, and the first derivative of bulk modulus (to fit to Murnaghan’s equation of state) of the related structures are calculated. The second-order elastic constants and the other related quantities such as Young’s modulus, shear modulus, Poisson’s ratio, sound velocities, and Debye temperature are also estimated. 相似文献
10.
J. K. Baria 《Czechoslovak Journal of Physics》2004,54(4):469-485
A model pseudopotential depending on an effective core radius but otherwise parameter free is used to study the interatomic
interactions, phonon dispersion curves (inq and r-space analysis), phonon density of states, mode Grüneisen parameters, dynamical elastic constants (C
11,C
12 andC
44), bulk modulus (B), shear modulus (C′), deviation from Cauchy relation (C
12–C
44), Poisson’s ratio (σ), Young’s modulus (Y), behavior of phonon frequencies in the elastic limit independent of the direction (Y
1), limiting value in the [110] direction (Y
2), degree of elastic anisotropy (A), maximum frequencyω
max, mean frequency 〈ω〉, 〈ω
2〉1/2=(〈ω〉/〈ω
−1〉)1/2, fundamental frequency 〈ω
2〉, and propagation velocities of the elastic constants in Cu, Ag, Au, Ni, Pd, and Pt. The contribution of s-like electrons
is calculated in the second-order perturbation theory for the model potential while that of d-like electrons is taken into
account by introducing repulsive short-range Born-Mayer like term. Very recently proposed screening function due to Sarkar
et al. has been used to obtain the screened form factor. The theoretical results are compared with experimental findings wherever
possible. A good agreement between theoretical investigations and experimental findings has proved the ability of our model
potential for predicting a large number of physical properties of transition metals. 相似文献
11.
S. Yu. Davydov 《Physics of the Solid State》2004,46(7):1200-1205
The pressure dependences of the second-order elastic constants C ij and the velocity of sound in 3C-SiC and 2H-SiC crystals are calculated in the framework of the Keating model. The third-order elastic constants C ijk for 3C-SiC are determined from the dependences of the second-order elastic constants C ij on the pressure p. 相似文献
12.
The dependences of the internal friction and the Young’s modulus defect of polycrystalline indium on the oscillatory strain
amplitude have been studied over a wide range of temperatures (7–320 K) and oscillatory strain amplitudes (10−7−3.5 × 10−4) at oscillatory loading frequencies of about 100 kHz. It has been revealed that the amplitude dependences of the internal
friction and the Young’s modulus defect include stages associated with the interaction of dislocations with point defects
and the interdislocation interaction. The temperature range characterized by the formation of point-defect atmospheres (the
Cottrell atmospheres) near dislocations in indium has been determined. 相似文献
13.
14.
The purpose of the present paper is to investigate the temperature and pressure dependences of the elastic properties of cerium dioxide using the statistical moment method (SMM). The equation of states of bulk CeO2 is derived from the Helmholtz free energy, and the pressure dependences of the elastic moduli like the bulk modulus, BT, shear modulus, G, Young’s modulus, E, and elastic constants (C11, C12, and C44) are presented taking into account the anharmonicity effects of the thermal lattice vibrations. In the present study, the influence of temperature and pressure on the elastic moduli and elastic constants of CeO2 has also been studied, using three different interatomic potentials. We compare the results of the present calculations with those of the previous theoretical calculations as well as with the available experiments. 相似文献
15.
A study of ultrasonic velocities and internal friction has been carried out in Pb-Bi alloys in the concentration range of
0 to 49.5 atomic % Bi using the composite oscillator technique. From the velocity and density data a set of elastic constants
namely, Young’s modulus, rigidity modulus, bulk modulus and Poisson’s ratio are estimated. The results are interpreted in
terms of the phase changes occurring in the alloy system. Internal friction is found to be more sensitive than the elastic
constants to the phase changes. 相似文献
16.
Abdelmadjid Bouhemadou 《Central European Journal of Physics》2009,7(4):753-761
Using First-principle calculations, we have studied the structural, electronic and elastic properties of M2TlC, with M = Ti, Zr and Hf. Geometrical optimization of the unit cell is in good agreement with the available experimental
data. The effect of high pressures, up to 20 GPa, on the lattice constants shows that the contractions are higher along the
c-axis than along the a axis. We have observed a quadratic dependence of the lattice parameters versus the applied pressure.
The band structures show that all three materials are electrical conductors. The analysis of the site and momentum projected
densities shows that bonding is due to M d-C p and M d-Tl p hybridizations. The M d-C p bonds are lower in energy and stiffer than M d-Tl p bonds. The elastic constants are calculated using the static finite strain technique. We derived the bulk and shear moduli,
Young’s modulus and Poisson’s ratio for ideal polycrystalline M2TlC aggregates. We estimated the Debye temperature of M2TlC from the average sound velocity. This is the first quantitative theoretical prediction of the elastic properties of Ti2TlC, Zr2TlC, and Hf2TlC compounds that requires experimental confirmation.
相似文献
17.
B. K. Kardashev T. S. Orlova B. I. Smirnov A. R. de Arellano-Lopez J. Martinez-Fernandez 《Physics of the Solid State》2010,52(10):2076-2081
The amplitude and temperature dependences of the Young’s modulus and the internal friction (ultrasonic absorption) of biomorphic
carbon, silicon carbide, and SiC/Si composite produced from medium density fiberboard (MDF) by pyrolysis (carbonization),
followed by infiltration of molten silicon into the prepared carbon preform have been studied in the temperature range 100–293
K in air and under vacuum. The measurements have been performed by the acoustic resonance method with the use of a composite
vibrator for longitudinal vibrations at frequencies of approximately 100 kHz. The data obtained by acoustic measurements of
the amplitude dependences of the elastic modulus have been used for evaluating the microplastic properties of samples under
study. It has been shown that the Young’s modulus, the decrement of elastic vibrations, and the conventional microyield strength
of the MDF samples differ from the corresponding data for previously studied similar materials produced from natural eucalyptus,
beech, sapele, and pine woods. In particular, the desorption of environmental molecules at small amplitudes of vibrations,
which is typical of biomorphic materials based on natural wood, is almost absent for the MDF samples. The results obtained
have been explained by different structures and the influence of pores and other defects, which, to a large extent, determine
the mechanical characteristics of the biomaterials under investigation. 相似文献
18.
This paper is mainly concerned with elastic and acoustic properties of vitrous silica besides the computation of phonon frequencies.
Thus the phonon frequencies of vitrous silica have been calculated assuming the electronic bulk modulus,K
e, as equal to zero. New equations have been derived to relate the pressure derivatives of second order elastic constants to
the acoustic Gruneisen’s parameters using both Bhatia-Singh’s parameters and Schofield’s equations. The calculated longitudinal
and transverse Gruneisen’s parameters and the predicted absorption band spectra from Nagendranath’s equation and Bhatia Singh’s
parameters are in good agreement with experiment. The calculated mean acoustic mode Gruneisen’s parameter evaluated from the
pressure derivative of Nagendranath’s equation is also in good agreement with experiment.
An erratum to this article is available at . 相似文献
19.
H.M. Ledbetter 《Ultrasonics》1985,23(1):9-13
For studying welds ultrasonically, the importance of knowing the material's single-crystal elastic constants, the Cijs, is explained. Where these constants are not known, some guidelines are given for estimating them from polycrystalline elastic constants such as Young's modulus and the shear modulus.The important case of [001] fibre texture is considered. Being transversely isotropic, this case exhibits five macroscopic elastic constants, which are related to the three cubic elastic constants: C11, C12, C44. From these five constants the angular variations of Young's modulus, the torsional modulus, and the sound velocities can be computed. For the same [001] fibre texture, results are given for a standard well-characterized material — copper, where the Cijs are well known. 相似文献
20.
The isotherms for the alkaline earth fluorides (CaF2, SrF2 and BaF2) have been computed using the expression for the total free energy of a crystal in the quasiharmonic approximation. The theoretical
points for SrF2 and BaF2 have been compared with the points derived from Bridgman’s experimental relation.
The temperature variation of the isothermal bulk modulus of the alkaline earth fluorides has been worked out on the basis
of Axe’s shell model. The theoretica points are compared with the points obtained from the temperature variation of the elastic
constants data. It is found that the vibrational contribution to the temperature variation of the elastic constants in these
crystals is significant. 相似文献