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Wyświetlanie 1-15 z 28
Tytuł:
Effect of Nucleation on the Stability of BCC Metals
Autorzy:
Verma, A.
Verma, M. L.
Rathore, R. P. S.
Powiązania:
https://bibliotekanauki.pl/articles/1963285.pdf
Data publikacji:
1997-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.Dc
Opis:
Numerical calculations are made of theoretical strength and range of stability of a perfect uniaxially stressed crystal lattice of bcc vanadium, niobium and tantalum in the framework of extended generalised exponential potential by applying Born stability criteria. Two ranges of stability, a bcc phase and a body centered tetragonal phase are found to exist. The computed values of theoretical strength and strain of bcc V, Nb and Ta agree reasonably well with the experimental limits.
Źródło:
Acta Physica Polonica A; 1997, 91, 3; 583-596
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phase Transitions and Stability of Group IV BCC Metals
Autorzy:
Verma, M. L.
Verma, A.
Rathore, R. P. S.
Powiązania:
https://bibliotekanauki.pl/articles/1968848.pdf
Data publikacji:
1998-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.Dc
Opis:
Born stability criteria were employed in the framework of extended generalised exponential potential to calculate the theoretical strength and range of stability of a perfect uniaxially stressed crystal lattice of group IV bcc metals: titanium, zirconium, and hafnium. The analysis depicts two ranges of stability, a bcc phase and a body centered tetragonal phase. The computed value of theoretical strength and strain of bcc Ti, Zr and Hf agree satisfactorily with the experimental limits. The second-order elastic constants C$\text{}_{11}$ and C$\text{}_{12}$ were also computed.
Źródło:
Acta Physica Polonica A; 1998, 93, 3; 479-489
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Elastic Behaviour and Lattice Vibrations in bcc V and Nb
Autorzy:
Verma, A.
Verma, M. L.
Rathore, R. P. S.
Powiązania:
https://bibliotekanauki.pl/articles/1946133.pdf
Data publikacji:
1996-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.Dj
62.20.Dc
Opis:
A model is developed by extending the generalised form of exponential potential known as extended generalised exponential potential to account for: (a) a realistic realization of interactions in all separations in general and that of small separations in particular, (b) three-body and electronic effects into the interaction in an alternative and simpler form, (c) a model free from usual fitting procedure. The model is employed to compute the cohesive energy, phonon spectra and second- and third-order elastic constants for group VA bcc metals V and Nb. The computed results showing good agreement with the experimental findings lend reliability and credibility to the potential.
Źródło:
Acta Physica Polonica A; 1996, 90, 3; 547-556
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Lattice Dynamics of Cubic Mercury Sulphide
Autorzy:
Szuszkiewicz, W.
Dybko, K.
Dynowska, E.
Górecka, J.
Witkowska, B.
Hennion, B.
Powiązania:
https://bibliotekanauki.pl/articles/1952186.pdf
Data publikacji:
1996-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.Dc
63.20.-e
Opis:
The acoustic phonon dispersion of mercury sulphide of zinc-blende structure (β-HgS) was studied by inelastic neutron scattering. The measurements were carried out at 19 K and 295 K on HgS crystals doped with Fe. A slight decrease in phonon frequencies with increasing temperature was found, the temperature dependence being the strongest for LA phonons with [ξ,ξ,0] propagation. From acoustic phonon dispersion the values of selected elastic constants were determined for β-HgS.
Źródło:
Acta Physica Polonica A; 1996, 90, 5; 947-950
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Elastic Constants of β-HgS
Autorzy:
Prieur, J. Y.
Joffrin, J.
Szuszkiewicz, W.
Dynowska, E.
Górecka, J.
Witkowska, B.
Powiązania:
https://bibliotekanauki.pl/articles/1992069.pdf
Data publikacji:
1998-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.Dc
64.60.My
Opis:
The elastic constants of single crystals of β-HgS highly doped with iron were directly determined at room temperature from the measurements of ultrasonic wave velocities by the pulse-echo technique. The values of c$\text{}_{11}$=6.750, c$\text{}_{12}$=5.186, and c$\text{}_{44}$=2.42 (given at 10$\text{}^{10}$ N m$\text{}^{-2}$ units) were obtained and compared with the experimental data taken for other mercury chalcogenides. The elastic characteristics of this group of materials is quite similar to those of Cd and Zn chalcogenides.
Źródło:
Acta Physica Polonica A; 1998, 94, 3; 487-491
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sound Attenuation at High Temperatures in Pt
Autorzy:
Singh, R. K.
Pandey, K. K.
Powiązania:
https://bibliotekanauki.pl/articles/2044642.pdf
Data publikacji:
2006-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.Dc
62.65.+k
Opis:
Ultrasonic attenuation due to phonon-phonon interaction and thermoelastic loss was evaluated in VIII group transition metal Pt in a wide temperature range (100 K to 1500 K) for longitudinal and shear waves along〈100〉, 〈110〉 and〈111〉 directions and for shear waves polarised along different directions. Electrostatic and Born-Mayer potentials were used to obtain second and third order elastic constants, taking nearest-neighbour distance and hardness parameter as input data. Second and third order elastic constants data obtained at different temperatures were used to obtain Gruneisen parameters and non-linearity or anisotropy parameters which in turn were used to evaluate (α/f$\text{}^{2}$)$\text{}_{l}$ and (α/f$\text{}^{2}$)$\text{}_{s}$ in Akhiezer regime. The results were discussed and it was found that at lower temperatures (α/f$\text{}^{2}$) increases rapidly with temperature and then rate of increase becomes very small. Contribution to the total attenuation due to thermoelastic loss is negligible so that due to phonon-phonon interaction establishing that major part of energy from sound wave is removed due to interaction with thermal phonons (lattice vibrations).
Źródło:
Acta Physica Polonica A; 2006, 109, 2; 219-228
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Orientation States in Rhombic NdGaO$\text{}_{3}$
Autorzy:
Savytskii, D. I.
Ubizskii, S. B.
Vasylechko, L. O.
Syvorotka, I. M.
Matkovskii, A. O.
Powiązania:
https://bibliotekanauki.pl/articles/1964528.pdf
Data publikacji:
1997-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.72.Mm
62.20.Dc
Opis:
The ferroelastic domain structure of NdGaO$\text{}_{3}$ is analyzed by three theories: group symmetry, tensor method and twinning by pseudosymmetry. The theories provide a coherent description of domain pairs and a determination of the position of W and S walls.
Źródło:
Acta Physica Polonica A; 1997, 92, 1; 231-236
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ultrasonic Attenuation in Dielectric Crystals
Autorzy:
Kor, S. K.
Singh, R. K.
Powiązania:
https://bibliotekanauki.pl/articles/1891964.pdf
Data publikacji:
1991-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.Dc
62.65.+K
Opis:
Ultrasonic attenuation and non-linearity parameters have been evaluated for dielectric crystals RbCl, RbBr and RbI in a wide temperature range. Basic physical parameters, nearest neighbour distance and hardness parameters of the substance and Coulomb and Born-Mayer potentials have been used to obtain ultrasonic attenuation due to phonon-viscosity mechanism along (100) direction of propagation for longitudinal and shear waves. Results are as expected and it has been concluded that ultrasonic attenuation is a fundamental property of the substance.
Źródło:
Acta Physica Polonica A; 1991, 80, 6; 805-810
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ultrasonic Attenuation in Alloys
Autorzy:
Kor, S. K.
Singh, R. K.
Powiązania:
https://bibliotekanauki.pl/articles/1929339.pdf
Data publikacji:
1993-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.Dc
62.65.+k
Opis:
Ultrasonic attenuation was evaluated in metallic alloys, Ni$\text{}_{x}$Cu$\text{}_{1-x}$ (x = 1.00, 0.70, 0.60, 0.45 and 0) due to phonon-phonon (p-p) interaction and thermoelastic loss in a wide temperature region along ⟨110⟩ crystallographic direction for longitudinal and shear waves. Ultrasonic Grüneisen parameters, nonlinearity constants and ultrasonic attenuation due to p-p interaction and thermoelastic loss were determined from 50 K to 500 K using the Born-Mayer and electrostatic potentials. The results were compared with available experimental results.
Źródło:
Acta Physica Polonica A; 1993, 83, 6; 751-758
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Reinforcement of Elastic Polymer Matrix Filled with Ultrafine Particles
Autorzy:
Kryszewski, M.
Bąk, G. W.
Powiązania:
https://bibliotekanauki.pl/articles/1968469.pdf
Data publikacji:
1997-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.Dc
81.20.Ti
Opis:
The nanofiller of noble metal may modify the properties of the polymer- noble metal composite even if the concentration of the metal nanoparticles is very low. The aim of this paper is to study the influence of colloidal particles in nanocomposites. For our studies we have selected polymethyl methacrylate-palladium nanocomposite. It is shown that the effective radius of the immobilised matrix environment is much greater than the radius of the palladium particles. Due to the binding of the matrix polymer and the palladium surface some volume of the surrounding matrix becomes immobilised giving rise to the effective increase in the size of the palladium filler. The analysis of a few models of nanocomposites used for interpretation of the mechanical properties has also been presented.
Źródło:
Acta Physica Polonica A; 1997, 92, 6; 1163-1167
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Anharmonic Properties of Alkali Halides and Cyanides
Autorzy:
Kailash, -
Powiązania:
https://bibliotekanauki.pl/articles/1943981.pdf
Data publikacji:
1996-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.Dc
81.40.Jj
Opis:
Anharmonic properties of 16 alkali halides and 4 alkali cyanides are investigated using long-range Coulomb and short-range Born-Mayer potentials starting from the nearest-neighbour distance and repulsive parameter. This study includes the prediction of second, third and fourth order elastic constants, the pressure derivatives of second and third order elastic constants and partial contractions at elevated temperatures. The results obtained in present investigations are in reasonable agreement compared with experimental studies.
Źródło:
Acta Physica Polonica A; 1996, 89, 1; 75-90
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Pressure Dependence of Elastic Constants in Zinc-Blende III-N and Their Influence on the Light Emission in Nitride Heterostructures
Autorzy:
Łepkowski, S. P.
Majewski, J. A.
Powiązania:
https://bibliotekanauki.pl/articles/2038098.pdf
Data publikacji:
2004-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.Dc
62.50.+p
Opis:
We studied the nonlinear elasticity effects for the case of III-N compounds. Particularly, we determined the pressure dependences of elastic constants, in zinc-blende InN, GaN, and AlN by performing ab initio calculations in the framework of plane-wave pseudopotential implementation of the density-functional theory. We found significant and almost linear increase in C$\text{}_{11}$, C$\text{}_{12}$ with pressure for considered nitrides compounds. Much weaker dependence on pressure was observed for C$\text{}_{44}$. We also discussed pressure dependences of two-dimensional Poisson's ratio and elastic anisotropy coefficient. Finally, we showed that the pressure dependence of elastic constants results in significant reduction of the pressure coefficient of the energy emission in cubic InGaN/GaN quantum wells and essentially improves the agreement between experimental and theoretical values.
Źródło:
Acta Physica Polonica A; 2004, 105, 6; 559-566
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Elastic Constants for Various Classes of Solids at High Temperature
Autorzy:
Liu, Q.
He, Q.
Powiązania:
https://bibliotekanauki.pl/articles/2047361.pdf
Data publikacji:
2007-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.Dc
91.60.Ki
Opis:
In the present communication, a new relationship for the temperature dependences of elastic constants are developed using a new expression for the temperature dependence of bulk modulus and the formulation derived from Tallon's model. The proposed relationship is applied to study elastic constants of NaCl, KCl, CaF$\text{}_{2}$, MgO, CaO, and Mg$\text{}_{2}$SiO$\text{}_{4}$. The result obtained for second-order elastic constants are found to compare well with the experimental data.
Źródło:
Acta Physica Polonica A; 2007, 112, 1; 69-76
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Elastic Properties of Zinc Blende MnTe
Autorzy:
Djemia, P.
Roussigné, Y.
Stashkevich, A.
Szuszkiewicz, W.
Gonzalez Szwacki, N.
Dynowska, E.
Janik, E.
Kowalski, B. J.
Karczewski, G.
Bogusławski, P.
Jouanne, M.
Morhange, J.
Powiązania:
https://bibliotekanauki.pl/articles/2038250.pdf
Data publikacji:
2004-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.Dc
75.50.Pp
78.35.+c
Opis:
The Brillouin light scattering was used to investigate elastic properties of the zinc blende, MBE-grown MnTe layer that was deposited on a (001) GaAs substrate covered by CdTe buffer layer. The three elastic constants of the zinc blende MnTe, namely c$\text{}_{11}$, c$\text{}_{12}$, and c$\text{}_{44}$, were directly determined for the first time from the frequency of the Rayleigh mode, of the pseudo-surface mode, and of the shear horizontal bulk mode traveling parallel to the layer surface. The value of c$\text{}_{11}$ was checked using the frequency of longitudinal bulk waves propagating at different angles from the normal of the layer plane. This value was also independently determined by results of the folding of acoustic phonons, observed for MnTe/CdTe superlattices by the Raman scattering. Finally, the bulk modulus given by the formula B=(c$\text{}_{11}$+2c$\text{}_{12}$)/3 was determined for zinc blende MnTe by ab initio calculations making use of the density functional theory and atomic pseudopotentials; spin polarization of MnTe was taken into account. A satisfactory agreement between theoretical and experimental values was obtained.
Źródło:
Acta Physica Polonica A; 2004, 106, 2; 239-247
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Singular Elastic Properties of Mixtures with the Re-entrant Nematic Phase
Autorzy:
Czechowski, G.
Jadżyn, J.
Powiązania:
https://bibliotekanauki.pl/articles/2038376.pdf
Data publikacji:
2004-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
64.70.Md
62.20.Dc
61.30.-v
Opis:
The paper presents temperature behavior of the splay and bend elastic constants measured for n-hexyloxycyanobiphenyl and n-octyloxycyanobiphenyl mixtures - a system exhibiting the re-entrant nematic phase. It was shown that singularities in the elastic properties of the system concern not only the nematic phase (the well-known pre-smectic effects) but first of all - the smectic A phase, in which the splay and bend deformations, normally not allowed for the layered structures, can be induced.
Źródło:
Acta Physica Polonica A; 2004, 106, 4; 475-485
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 28

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