共查询到20条相似文献,搜索用时 31 毫秒
1.
Summary The vibrational spectrum and one-phonon density of states of a chalcopyrite crystal AgGaS2 are calculated in an extended Keating’s model with two-bond-stretching and one-bond-bending force constants. Three charges
of ions and three force constants are determined by a least-square fitting to experimental frequencies of long-wave phonons
taken from Raman-scattering experiments. The calculated constant-volume specific heat, Debye temperature and elastic constants,
of AgGaS2 are in agreement with the experimental data of other authors. 相似文献
2.
A calculation is made of the long-wavelength phonon spectrum of ZnGeP2 and AgGaS2 in the hard ion model. The parameters of short-range forces and dynamic charges are found by comparing the theory with the experimental data on infrared absorption and Raman scattering of light. The elastic and piezoelectric constants are calculated. The available experimental data are discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 3–10, May, 1980. 相似文献
3.
The low-frequency dielectric tensor is calculated for AIIBIVC
2
V
and AIBIIIC
2
VI
crystals in terms of the long-wave frequencies of lattice vibrations, corresponding to various orientations of the wave vector. The qualitative shape of the spectrum of mechanical polaritons is obtained. The coefficient of light reflection is calculated as a function of the frequency and direction of propagation for a CdGeP2 crystal.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 39–43, June, 1978. 相似文献
4.
The absolute orientation of single crystals of ZnGeP2 and AgGaS2 on which the relative sense of the d14 and d36 piezoelectric coefficients had been measured, was determined by the X-ray absorption edge method. Both coefficients were thereby found to be positive, corresponding in the point charge model to positive charge associated with the metal and negative charge with the nonmetal atoms, in contrast with the negative d33′ reported in GaP. 相似文献
5.
Polarized IR reflection spectra of Li2B4O7 crystals are studied in a spectral range of 80–1600 cm?1 and compared with their Raman spectra. Based on the results of the dispersion analysis of the spectra, the frequencies, damping constants, and oscillator strengths of all vibrations are determined. The inversion of frequencies of the longitudinal and transverse vibrations of the A 1 and E symmetry in a range of 900–1150 cm?1 is found. Based on the data thus obtained, the effective charges are calculated and the types of chemical bonds are analyzed for structural groups of the Li2B4O7 crystal. 相似文献
6.
J. Tilgner I. Topol G. Leonhardt A. Meisel 《Journal of Physics and Chemistry of Solids》1975,36(1):27-30
By means of a double crystal spectrometer and a computer the chemical shifts of the Ga Kα1,2, As Kα1,2 and Kβ1,3 lines were determined with high accuracy. An interpretation of the results obtained with a free ion model and a calculation according to the Hartree method shows agreement of the values calculated for the effective atomic charges with those based on chemical experience, and also the presence of a charge transfer from the A atom to the B atom in AIIIBV compounds. The existence of binding charges is one of the reasons for the fact that |qA| ≠ |qB|. The interpretation of the Kβ1,3 and Lα shifts shows the limitations of the free ion model. 相似文献
7.
A. V. Vdovin V. N. Moiseenko V. S. Gorelik Ya. V. Burak 《Physics of the Solid State》2001,43(9):1648-1654
The polarized infrared reflection spectra of Li2B4O7 were studied in the spectral range 80–1600 cm?1 and compared with Raman spectra. From the spectrum dispersion analysis, the frequencies, damping, and dielectric oscillator strengths were determined for all vibrational modes observed. A calculation of the effective charges and an analysis of the chemical-bond types of the Li2B4O7 crystal structural units were carried out on the basis of the obtained data. 相似文献
8.
《Journal of Physics and Chemistry of Solids》2003,64(9-10):1801-1805
Photoluminescence (PL) related to rare-earth (RE) impurities (Ho, Er and Eu) in AgGaS2 and CuGaS2 crystals has been studied. In Ho-doped AgGaS2 and CuGaS2, two series of PL lines are observed in 1.86–1.92 eV region and 2.24 eV region, and they are assigned to 5F3–5I7 and 5S2–5I8 transitions of the Ho3+ ion, respectively. Similarly, in Er-doped AgGaS2 and CuGaS2, Er3+-related two PL series are observed: 1.83–1.88 eV region (4F9/2–4I15/2) and 2.22–2.26 eV region (4S3/2–4I15/2). For both Ho and Er impurities, the profile of the PL spectrum in AgGaS2 is complex, and PL exhibited large number of lines compared with that in CuGaS2. The differences in PL spectra between this two compounds are related to the crystal field at the cation site and the local atomic arrangement of the RE impurities. This work also refers to the PL band at 2.28 eV observed for the Eu-doped AgGaS2 crystal. 相似文献
9.
Ying-Fei Zhang Zhi-Hui Kang Yun Jiang Yury M. Andreev Konstantin A. Kokh Anna V. Shaiduko 《Optics Communications》2011,284(6):1677-1681
We report a systematic study of AgGaS2- and Al-doped GaSe crystals in comparison with pure GaSe and S-doped GaSe crystals. AgGaS2-doped GaSe (GaSe:AgGaS2) crystal was grown by Bridgman technique from the melt of GaSe:AgGaS2 (10.6 wt.%). Its real composition was identified as GaSe:S (2 wt.%). Al-doped GaSe (GaSe:Al) crystals were grown from the melt of GaSe and 0.01, 0.05, 0.1, 0.5, 1, 2 mass % of aluminium. Al content in the grown crystals is too small to be measured. The hardness of GaSe:S (2 wt.%) crystal grown from the melt of GaSe:AgGaS2 is 25% higher than that of GaSe:S (2 wt.%) crystal grown by a conventional S-doping technique and 1.5- to 1.9-times higher than that of pure GaSe. GaSe:Al crystals are characterized by 2.5- to 3-times higher hardness than that of pure GaSe and by extremely low conductivity of ≤ 10− 7 Om− 1 cm− 1. A comparative experiment on SHG in AgGaS2-, Al-, S-doped GaSe and pure GaSe is carried out under the pumps of 2.12-2.9 μm fs OPA and 9.2−10.8 μm ns CO2 laser. It was found that GaSe:S crystals possess the best physical properties for mid-IR applications among these doped GaSe crystals. GaSe:Al crystals have relatively low conductivity which have strong potential for THz application. 相似文献
10.
A. A. Galeev N. M. Khasanova A. V. Bykov G. R. Bulka V. M. Vinokurov N. M. Nizamutdinov 《Applied magnetic resonance》1996,11(1):61-86
Dopant Fe3+ ions in tetrahedral and octahedral positions of Ge4+ in the crystal Li2Ge7O15 were studied using EPR. Fe3+ substitutes for Ge4+ with a local charge compensation. The octahedral site and the tetrahedral sites significantly differ by the value of the invariant sumS(B 4) of theB 4 tensor of the spin Hamiltonian of Fe3+. The irreducible tensor products {V 4 ? V 4}4 and {V 4?V 4}2 theV 4 tensor of the crystal field calculated using the point-charge model for octahedral and tetrahedral complexes provide the predominant contribution of the crystal field to theB 4 andB 2 tensors of the spin Hamiltonian of Fe3+, respectively. A comparison of the fourth-rank tensorsB 4 of the spin Hamiltonian and {V 4?V 4}4 of the crystal field determined at 300 K with those determined at 77 K supports the conclusion that the phase transition is accompanied by combined rotation of the [GeO4] tetrahedra with the [Ge(1)O6] octahedron almost unaltered. The spectrum lines are narrow and the variety of point defects in the vicinity of the paramagnetic impurity ions Fe3+, Cr3+ and Cu2+ is not detected. These facts are inconsistent with the statistically distributed model for the Li(2) atom. In specific cases at 300 K, when the wings of the two spectrum lines of theM→M+1 and theM+2 →M+3 transitions of Fe3+ ions belonging to one system of translationally equivalent positions overlap an extra line appears in the center between these lines. It is suggested that this effect is due to the soft phonon mode above the phase transition temperature. 相似文献
11.
Analysis is given for a possibility of singly resonant parametric oscillation in the submillimeter range at synchronous pumping
of the ZnGeP2 crystal by a train of 100-ps second-harmonic pulses from the CO2 laser with the radiation energy 1.0 J. The calculation shows that using the ZnGeP2 crystal and the second harmonic of the CO2 laser with the energy density 1.8 J cm−2, one can get the peak submillimeter radiation power from 3.6 to 12 MW in the range from 95 to 300 μm (1.0–3.3 THz). The expected
peak power values are larger than the experimental ones obtained by other nonlinear optics methods. 相似文献
12.
Published experimental frequencies are used to calculate Urey-Bradley force fields and ionic charges of some ABS2 chalcopyrite compounds. The values obtained for the A?S and B?S force constants as well as the ionic charges are discussed. 相似文献
13.
The coupled, two-variable integral equations that determine the 4ΛHe and 4ΛH bound states, when the NN and ΛN interactions are represented by separable potentials, are derived from the Schrödinger equation. The integral equations are solved numerically for simple s-wave potentials and for tensor potentials in the truncated t-matrix approximation without resort to separable expansion of the kernels. The Λ-separation energy difference ΔBΛ resulting from the genuine four-body model is shown to be approximately twice as large as that coming from an “effective two-body” model calculation, when identical central potentials are used. The four-body model estimate of ΔBΛ made with tensor forces is consistent with the experimental value, indicating that charge symmetry breaking implied by the low energy Λ N scattering parameters is compatible with that suggested by the known binding energy difference in the A = 4 hypernuclear isodoublet. 相似文献
14.
S. Sugai 《Solid State Communications》1982,44(8):1141-1143
Lattice vibrations in 2H-TaSe2 have been reinvestigated by Raman scattering in view of the recent orthorhombic structure of the commensurate charge density wave (CCDW) phase. The renormalization of six charge density waves on two layers gives four Ag modes and two B1g modes in the orthorhombic CCDW phase, in place of two A1g modes and two E2g modes in the hexagonal CCDW phase which had been believed. The splitting of the E2g modes to the Ag and B1g modes in the orthorhombic symmetry depends on the interlayer interaction. The observed small splitting less than 3 cm-1 shows the weak interlayer interaction. The energies of the four Ag modes and the two B1g modes are presented as a function of temperature. 相似文献
15.
V. G. Voevodin A. I. Gribenyukov A. N. Morozov V. S. Morozov 《Russian Physics Journal》1985,28(2):144-148
Results from a study of electrophysical and luminescent properties of zinc-germanium diphosphide single crystals, diffusion doped with copper, are presented. The nature of the dominant defects formed upon copper diffusion in ZnGeP2 is determined using a thermodynamic analysis of defect formation processes in ZnGeP2 and a ZnGeP2: Cu solid solution performed within the framework of the quasichemical analysis method. It is demonstrated that by choosing the copper diffusion method the hole concentration in the ZnGeP2 can be varied over the range 1012–1016 cm–3. A retrograde character was observed in copper solubility in ZnGeP2 compounds. Defect formation processes in ZnGeP2 upon copper diffusion depend on the degree of atomic ordering in the cation sublattice at the diffusion annealing temperature.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 64–69, February, 1985. 相似文献
16.
The results of the energy band structure calculations of A2B4C25 compounds are reviewed, and the differences in the energy spectra passing from A3B5 semiconductors to their closest ternary analogs are described. The origin of the lowest conduction band minima of A2B4C25 compounds was determined from the slopes of the fundamental absorption edge and the pressure coefficients of the energy gap. The investigations of the valence band structure from electroreflectance (ER), thermoreflectance (TR) and wavelength modulated absorption (WMA) spectra are reviewed. In the higher energy region the ER and TR spectra of A2B4C25 compounds were found to be more complicated in comparison with those of their binary analogs. A model of an assignment of the structures in optical spectra of A2B4C25 compounds is discussed. 相似文献
17.
In this paper we present an expression relating the cohesive energy (E coh in kcal/mol) of AIIIBV and AIIBVI semiconductors with the product of ionic charges (Z 1 Z 2) and nearest-neighbour distance d (Å). The cohesive energy values of these solids exhibit a linear relationship when plotted on a log-log scale against the nearest-neighbour distance d (Å), but fall on different straight lines according to the ionic charge product of the solids. A good agreement has been found between the experimental and calculated values of the cohesive energy of AIIIBV and AIIBVI semiconductors. 相似文献
18.
A. A. Ionin I. O. Kinyaevskii Yu. M. Klimachev 《Bulletin of the Lebedev Physics Institute》2014,41(8):222-225
The phase matching conditions in the ZnGeP2 crystal are calculated and analyzed from the viewpoint of broadband frequency conversion of mid-IR radiation. The frequency conversion of Cr:ZnS laser radiation in the ZnGeP2 crystal is calculated. The results show the possibility of developing a broadband laser source whose spectrum spans a wavelength range of 3.2–9.5 µm. 相似文献
19.
In this paper we present an expression relating the lattice thermal expansion coefficient αL (10−6 K−1) for the AIIIBV and AIIBVI semiconductors with the product of ionic charges (Z1Z2), melting temperature (Tm) and nearest neighbor distance d (Å). The lattice thermal expansion coefficient of these compounds exhibit a linear relationship when plotted on a log–log scale against the melting temperature (Tm), but fall on different straight lines according to the ionic charge product of the compounds. A good agreement has been found between the experimental and calculated values of the lattice thermal expansion coefficient for AIIIBV and AIIBVI semiconductors. 相似文献
20.
F. Gervais 《Solid State Communications》1976,18(2):191-198
Effective charges in non-cubic binary oxide crystals are evaluated on the basis of their transverse and longitudinal optical phonon frequencies. The temperature dependence of the effective charge is reported in quartz, rutile and corundum. Three procedures which allow the determination of effective charges in ternary compounds are presented and applied to halogenate, silicate, aluminate and ABOn-type crystals, where A is an alkali or alkaline earth and B is a transition-metal element. Results are compared with Phillips's ionicities. 相似文献