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Wyświetlanie 1-15 z 51
Tytuł:
Determination of Vibrational Eigenfrequencies of Semiconductors Using Tight-Binding Total Energy Calculations
Autorzy:
Stephan, J.
Suisky, D.
Powiązania:
https://bibliotekanauki.pl/articles/1952702.pdf
Data publikacji:
1996-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.-e
Opis:
We calculate the eigenfrequencies of bulk semiconductors using tight-binding total energy calculations of an ideal and a distorted lattice. We correlate the obtained energy change with the harmonic force constants appearing as parameters in the expansion of the potential energy of the crystal lattice in terms of the displacement. A good agreement of the calculated q = 0 optical vibrational modes with the experimental values for Si, Ge, GaAs and GaP bulk crystals is obtained. The influence of a surface on the force constants and the vibrational frequencies is studied.
Źródło:
Acta Physica Polonica A; 1996, 90, 5; 1075-1079
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phonon Dispersion in Cu-Zn Alloy
Autorzy:
Akgün, I.
Powiązania:
https://bibliotekanauki.pl/articles/1929818.pdf
Data publikacji:
1993-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.-e
Opis:
Phonon dispersion curves for fcc Cu-25% Zn alloy were calculated using deLauney angular force model, the analysis being limited to the second neighbour interactions only. In the present calculations the elastic constants of Cu and Zn in fcc and hcp phases, respectively, were used to evaluate the force constants of the alloy system. Satisfactory agreement between theory and experiment is obtained.
Źródło:
Acta Physica Polonica A; 1993, 84, 6; 1055-1058
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Lattice Dynamics of Ni-24%Fe Alloy Based on an Empirical Many-Body Potential
Autorzy:
Akgün, İ.
Uğur, G.
Powiązania:
https://bibliotekanauki.pl/articles/2011071.pdf
Data publikacji:
1999-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.-e
Opis:
We have developed an empirical many-body potential and used it to investigate the dynamical behaviours of fcc Ni-24%Fe alloy. The new many-body potential contains both two- and three-body atomic interactions. The two-body potential is expressed by the modified form of the generalized Morse potential and the three-body potential is developed based on the new two-body model potential. The parameters defining the many-body potential for Ni and Fe were computed following a procedure similar to the method defined by Akgün and Uğur for fcc structure at the lattice constant of the alloy. The radial, tangential and three-body force constants of the alloy were calculated by the concentration averages of the computed force constants of the component metals. Finally, the phonon frequencies of the alloy along the principal symmetry directions were computed using the calculated two- and three-body force constants. The theoretical results were found to be in good agreement with the corresponding experimental values.
Źródło:
Acta Physica Polonica A; 1999, 96, 3-4; 391-398
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Lattice Dynamical Calculations for $Li_{1+x}Ti_{2-x}O_4$ (x=0.33) and $Li_{1-y}Mg_{y}Ti_2O_4$ (y=0.1, 0.3)
Autorzy:
Kushwaha, A.
Powiązania:
https://bibliotekanauki.pl/articles/1399286.pdf
Data publikacji:
2013-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.-e
Opis:
Zone-centre Raman and infrared phonon frequencies for the spinel phases of oxides $Li_{1+x}Ti_{2-x}O_4$ (x=0.33) and $Li_{1-y}Mg_{y}Ti_2O_4$ (y=0.1, 0.3) of space group Fd3m have been calculated using a proposed short-range force constant model. In this model, the lattice potential energy is expanded using Taylor's expansion in the harmonic approximation. The calculated zone-centre phonon frequencies are in good agreement with the available experimental and previously calculated results.
Źródło:
Acta Physica Polonica A; 2013, 124, 4; 695-697
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Lattice Dynamical Calculations for Inverse Spinel Compounds
Autorzy:
Kushwaha, A.
Powiązania:
https://bibliotekanauki.pl/articles/1398877.pdf
Data publikacji:
2015-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.-e
Opis:
Lattice dynamical calculations have been performed for inverse spinel structure compounds $MIn_{2}S_{4}$ (M = Mn and Co) using the proposed six parameter bond-bending force constant model. In this model, the short-range force constant is calculated by using the Taylor expansion of the potential energy in the harmonic approximation. This model is applied to study the zone-centre (Γ=0) phonon frequencies of inverse spinels $MIn_{2}S_{4}$ (M = Mn and Co). The significant outcome of the present work is that the second neighbor interactions (octahedral bonding) are stronger than the first neighbor interactions (tetrahedral bonding). The zone-center phonon frequencies, calculated using these parameters, are found to be in very good agreement with the observed results.
Źródło:
Acta Physica Polonica A; 2015, 127, 3; 741-743
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:
Ab Initio Lattice Dynamics of MgB$\text{}_{2}$
Autorzy:
Parlinski, K.
Powiązania:
https://bibliotekanauki.pl/articles/2028971.pdf
Data publikacji:
2001-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.-e
74.20.-z
Opis:
Using the density functional theory, the phonon dispersion relations, the phonon density of states, mean square displacements, and thermodynamic functions of superconducting MgB$\text{}_{2}$ crystals have been calculated. The modes of graphite-like boron network belong to optic phonon branches, which are rather independent of the Mg vibrations.
Źródło:
Acta Physica Polonica A; 2001, 100, 5; 767-772
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Lattice Dynamics of Noble Metals on Effective Three-Body Interaction
Autorzy:
Coelho, A. A.
Shukla, M. M.
Powiązania:
https://bibliotekanauki.pl/articles/1945409.pdf
Data publikacji:
1996-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.-e
65.40.-f
Opis:
Quite recently we modified the original model of Sarkar et al. for cubic metals in extending the ion-ion interaction, ion-electron interaction and the introduction of crystal equilibrium condition. We applied our scheme to alkali metals. We studied here the lattice dynamics of noble metals on our approach by calculating phonon dispersion relations along the three principal symmetry directions, [ξ00], [ξξ0] and [ξξξ] and the (θ-T) curves of three noble metals: copper, silver and gold. We obtained reasonable agreement with the experimental findings.
Źródło:
Acta Physica Polonica A; 1996, 89, 5-6; 615-623
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Characterization and Selected Physical Properties of CdTe/MnTe Short Period Strained Superlattices
Autorzy:
Szuszkiewicz, W.
Dynowska, E.
Bąk-Misiuk, J.
Karczewski, G.
Wojtowicz, T.
Kossut, J.
Jouanne, M.
Powiązania:
https://bibliotekanauki.pl/articles/1952708.pdf
Data publikacji:
1996-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.-e
78.30.Fs
Opis:
Phonon excitations in (CdTe)$\text{}_{12}$/(MnTe)$\text{}_{n}$ (100) superlattices (n=2, 4, 8) were investigated at 295 K and 25 K with the use of Raman scattering. From the "folded" phonon frequencies the elastic constant c$\text{}_{11}$ value for MnTe was estimated. The strain arising from lattice mismatch (determined by X-ray diffraction) results in shifts of MnTe and CdTe "confined" LO phonon frequencies. For the precise determination of LO phonon dispersions an additional shift due to Mn diffusion at the CdTe/MnTe interface should be taken into account.
Źródło:
Acta Physica Polonica A; 1996, 90, 5; 1090-1094
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Correlated Thermal Vibrations on Temperature Dependence of Surface Peak
Autorzy:
Gwizdałła, T.
Czerbniak, J.
Powiązania:
https://bibliotekanauki.pl/articles/1943974.pdf
Data publikacji:
1996-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.80.Mk
63.20.-e
Opis:
The influence of correlation between thermal displacements of atoms in string on the calculated Rutherford backscattering spectra under channelling conditions was studied. This correlation was incorporated into the existing Monte Carlo computer code by means of sampling the displacements from distribution transformed by the variance-covariance matrix. Various methods of implementing the correlation into calculation were used. As a result the deformation of energy spectrum was obtained. The explicit decrease in surface peak due to the correlation was observed. The significance of this effect decreases with increasing temperature. Calculation were performed in a wide region of temperatures, up to the melting point.
Źródło:
Acta Physica Polonica A; 1996, 89, 1; 61-67
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Lattice Dynamics of Alkali Metals in a Three-Body Interaction
Autorzy:
Coelho, A. A.
Shukla, M. M.
Powiązania:
https://bibliotekanauki.pl/articles/1932113.pdf
Data publikacji:
1995-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
65.40.-f
63.20.-e
Opis:
The original model of Das et al. is modified in extending the electron-ion interaction on a three-body forces and including the crystal equilibrium condition to reduce one independent parameter. We studied the phonon dispersion relations along the three principal symmetry directions i.e. [ξ,0,0], [ξ,ξ,0] and [ξ,ξ,ξ] and θ-T curves of alkali metals, Na, K, Rb, Cs and Li. There is close agreement between the computed results and the experimental observations.
Źródło:
Acta Physica Polonica A; 1995, 87, 3; 599-609
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Pre-Melting in Cubic Structure with Relaxation
Autorzy:
Gwizdałła, T.
Czerbniak, J.
Powiązania:
https://bibliotekanauki.pl/articles/1992928.pdf
Data publikacji:
1998-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.-e
68.35.Ja
Opis:
We study the effect of melting of well-defined crystal surface within the frame of theory of atomic vibrations in harmonic approximation. We find that for two types of cubic crystal lattice: face centered cubic and body centered cubic, we may expect the existence of pre-melting. It is also shown that the occurrence or absence of surface melting depends strongly on the relaxation of lattice constant.
Źródło:
Acta Physica Polonica A; 1998, 94, 5-6; 785-793
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Reflectivity Studies of Lattice Vibrations and Free Electrons in MBE Grown GaN Epitaxial Layers
Autorzy:
Iller, A.
Jantsch, W.
Marks, J.
Pastuszka, B.
Diduszko, R.
Powiązania:
https://bibliotekanauki.pl/articles/1969092.pdf
Data publikacji:
1998-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.-e
78.66.Fd
Opis:
We have observed a sharp structure with a peak at the frequency of the E$\text{}_{1}$-TO phonon in the reflectivity of GaN epitaxial layers grown by molecular beam epitaxy on Si substrates. The simulations of the reflection performed show that the observed shape can be explained by assuming both collective lattice vibrations and free carriers contributions to the dielectric function. We assumed the Lorentz oscillator to describe the contribution of the collective lattice vibrations and the Drude-Lorentz model for that of free carriers. Fitting the calculated reflectivity to the spectrum obtained experimentally allowed us to evaluate lattice and free carrier parameters.
Źródło:
Acta Physica Polonica A; 1998, 94, 2; 336-340
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An Investigation of Optical Vibrations in Zn$\text{}_{3}$P$\text{}_{2}$
Autorzy:
Misiewicz, J.
Wrobel, J. M.
Clayman, B. P.
Powiązania:
https://bibliotekanauki.pl/articles/1887203.pdf
Data publikacji:
1991-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.-e
78.30.Hv
Opis:
Reflectivity and transmittivity spectra of Zn$\text{}_{3}$P$\text{}_{2}$ in the far infrared region were measured at several temperatures. Raman scattering spectra at 295 K were also measured. Results of these measurements were interpreted in terms of one-phonon and multi-phonon transitions.
Źródło:
Acta Physica Polonica A; 1991, 79, 2-3; 405-409
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ab initio Calculations of Phonon Dispersion Relations in Aluminium
Autorzy:
Scharoch, P.
Parliński, K.
Kiejna, A.
Powiązania:
https://bibliotekanauki.pl/articles/2012957.pdf
Data publikacji:
2000-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.-e
71.15.Nc
Opis:
A direct method and ab initio force constants were used to calculate phonon dispersion curves and phonon density in Al. The force constants were determined from the Hellmann-Feynman forces induced by the displacement of an atom in the 2×2×2 fcc crystallographic supercell. This size of the supercell gives exact phonon frequencies at Γ, X, L, W points of the Brillouin zone. The calculated phonon dispersion curves are in good agreement with the experimental data.
Źródło:
Acta Physica Polonica A; 2000, 97, 2; 349-354
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 51

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