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141.
The phonon spectra of unstrained and strained quasiperiodic semiconductor superlattices (QSSL) have been calculated using
one-dimensional linear chain model. We consider two types of quasiperiodic systems, namely cantor triadic bar (CTB) and Fibonacci
sequences (FS), constituting of AlAs, GaAs and GaSb of which the latter two have a lattice mismatch of about 7%. The calculations
have been made using transfer matrix method and also with and without the inclusion of strain. We present the results on phonon
spectra of two component CTB and two as well as three component FS semiconductor superlattices (SSL), thickness and order
dependence on LO mode of GaAs, effect of strain on LO frequency of GaAs. The calculated results show that the strain generated
due to lattice mismatch reduces significantly the magnitudes of the confined optical phonon frequency of GaAs. 相似文献
142.
We have investigated the lattice vibrational properties of a two-component strained layer semiconductor superlattice (GaAs)
n1 (GaSb)
n2 using a one-dimensional linear chain model and transfer matrix method [1]. Effect of strain, arising due to the lattice mismatch
(∼ 7%) has been considered explicitly in the equation of motion. We show for the first time that the optical vibrational frequency
increases (in the case of (GaAs)4 (GaSb)
n
) or decreases (in the case of (GaAs)
n
(GaSb)4) with increase of layer thicknessn, in either type of superlattices. Raman scattering measurements on some other similar systems support our findings. 相似文献
143.
We have calculated the phonon and periodon dispersion relations in IV–VI semi-conducting bulk PbTe and SnTe and their superlattice
structure. The model used here is a one-dimensional lattice which includes harmonic interactions up to second neighbours as
well as on-site nonlinear electron-ion interactions at the anion site. We calculate the phonon and periodon dispersion relations
in bulk and PbTe-SnTe superlattice for the transverse optic and acoustic modes using the transfer matrix method. Our analysis
has predicted correct nature of the folding of acoustic and confinement of optical phonons at various frequency intervals
corresponding to pass and stop bands of the superlattices. 相似文献
144.
Differential cross sections, vector and tensor analysing powers have been measured for the 61Ni(d, p) reaction at a deuteron energy of 12.3 MeV. Most of the 30 transitions observed below 8.5 MeV excitation are dominated by a single j-value, which was determined from behaviour of the analysing power data. For a number of transitions it was possible to make unambiguous j-assignment relying on the established j-dependence of the T22 tensor analysing power. The deduced spectroscopic factors indicate that the full strength of neutron transfer to the () and orbits was found and seven transitions were located above 5.3 MeV. The separated strengths of the transitions are compared with shell-model calculations for the low-lying states of 62Ni. 相似文献
145.
146.
Kamal K. Bharadwaj Mohan K. Kadalbajoo R. Sankar 《Applied mathematics and computation》1984,15(2):137-149
The symmetric marching technique has been developed to solve the Poisson equation with Dirichlet boundary conditions. The method has been combined with a mesh refinement technique, which is used as an appropriate interpolation scheme to obtain a solution of the problem on finer grids. The effectiveness of the method has been demonstrated by solving some test examples. 相似文献
147.
M. Dakshinamoorthy K. Iyakutti S. Sankar R. Asokamani 《Zeitschrift für Physik B Condensed Matter》1984,55(4):299-308
The electronic bandstructures of rare earth metal Praseodymium (Pr) have been calculated for a wide range of static pressures using RAPW method. The density of states and Fermi surface cross sections on the principal planes corresponding to various pressures are obtained. It is seen that, there is, 4f shell breakdown in Pr under pressure and formation of 4f bands. The calculation of the superconducting transition temperaturesT
c
corresponding to various pressures shows that Pr may become a high pressure superconductor like Cerium eventhough it is not observed experimentally to be a superconductor because of its magnetic character at normal pressure. 相似文献
148.
The specific heat of superconducting oxide compound, YBa2Cu3O7 ?x , is studied using a quasi-adiabatic calorimeter from 4.2 to 60 K. The analysis of the specific heat data below 15 K gives a value of 17 mJ/mole K2 for the electronic heat capacity coefficient. The value ofθ D(0) is determined to be 397±8 K. The variation ofθ D with temperature was calculated in the temperature range 4.2 to 60 K. 相似文献
149.
High concentrations of silica in rocks are determined by means of the stable α-12-molybdosilicic acid formed at around pH 4.2 in acetate buffer. Phosphate interference is avoided by acidification with sulphuric acid. Silica is quantified by differential spectrophotometry at 400 nm against standard rock solutions. Considerable amounts of phosphorus, arsenic and titanium and small amounts of germanium and vanadium do not interfere. The standard deviation is about 0.3%. The method is rapid and suitable for routine analysis of silicate and phosphate rocks. 相似文献
150.
The softening of the IR active 300 cm−1 phonon mode in Tl-2223 superconductor, aroundT
c has been explained by considering a sixth order polarization potential at the off-center oxygen ion site in the Tl-O plane,
and by using a nonlinear lattice dynamical theory. The present theory explains, more or less satisfactorily, the unusual temperature
dependence of oxygen ion vibration and frequency shifts at higher temperature. The existence of strong nonlinear electron-phonon
interaction atT
c has been emphasized. 相似文献