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1.
N.Sreedhara Murthy T. Manisekaran N.S. Bapat 《Journal of Quantitative Spectroscopy & Radiative Transfer》1983,29(2):183-187
The RKRV turning points for the ground states of SrO, SnCl, NaH, and RbH have been calculated. The dissociation energies of the ground states have been obtained by curve fitting using an empirical potential function with the RKRV potential energy curves. The estimated values of the dissociation energies are 4.72±0.11, 2.9±0.13, 2.36±0.08, and 2.14±0.07 for SrO, SnCl, NaH, and RbH, respectively. 相似文献
2.
N. Sreedhara Murthy S.P. Bagare B. Narasimha Murthy 《Journal of Quantitative Spectroscopy & Radiative Transfer》1978,19(4):455-459
The true potential energy curve for the ground state of AlO has been extended up to the observed vibrational levels v = 22 using revised vibrational constants. The dissociation energy for the ground state of AlO has been estimated to be 4.15 ± 0.05 eV by the method of curve fitting. The Lippincott potential function has been used for fitting with the RKRV curve. 相似文献
3.
N.Sreedhara Murthy N.S. Bapat T. Manisekaran 《Journal of Quantitative Spectroscopy & Radiative Transfer》1983,30(4):381-383
A method is proposed for estimation of the vibrational anharmonicity constants ωeχe of diatomic molecules. The procedure involves fitting of the potential energy curve obtained by the RKRV method with that obtained by using the 5-parameter Hulburt-Hirschfelder potential function. We have predicted values of ωeχe for alkali halides for which accurate data are not available. 相似文献
4.
Turning points of the vibrating BeCl molecule in the A2IIr and X2Σ+ electronic states are evaluated using the RKRV potential. The Franck-Condon factors and r-centroids have been computed for the A2IIr → X2Σ+ transition using wave functions appropriate to the RKRV potential curve. The results are consistent with the intensity distribution in the vibrational bands for the specified transition. The sequence difference Δ remains approximately constant for the r-centroids. 相似文献
5.
V.M. Rao M.L.P. Rao P.T. Rao 《Journal of Quantitative Spectroscopy & Radiative Transfer》1981,25(6):547-549
The dissociation energy of the ground state of the CuH molecule, which is observed in sun spots and in 19 Piscium, has been evaluated by fitting the Hulburt-Hirschfelder function to the RKRV curve. It is shown that the Hulburt-Hirschfelder potential reproduces the true curve more accurately than does the Loppincott function. The D0 value obtained in the present study is 2.84eV, while the values reported by Herzberg and Beckel et al. are <2.89 and 2.80 ±0.12eV, respectively. 相似文献
6.
Based on density functional theory, we perform first-principles investigations to study the optical properties of the O-, F- and H-terminated SiC nanoribbons with armchair edges (ASiCNRs). By irradiating with an external electromagnetic field, we calculate the dielectric function, reflection spectra, energy loss coefficient and the real part of the conductance. It is demonstrated that the optical constants are sensitive to the low-energy range, different terminal atoms do not make much difference in the shape of the curves of the optical constants for the same-width ASiCNR, and the optical constants of wider nanoribbons usually have higher peaks than that of the narrower ones in low energy range. We hope that our study helps in experimental technology of fabricating high-quality SiC-based nanoscale photoelectric device. 相似文献
7.
Some phonon dispersion curves in ZnO have been determined by inelastic neutron scattering. Shell model calculations with 10 parameters were fitted to the neutron data, to optical frequencies and to dielectric constants. Good agreement was obtained including some elastic constants which were calculated from the model. 相似文献
8.
Rajendra Gupta 《Journal of Physics and Chemistry of Solids》1979,40(8):579-584
The lattic dynamics of covalent crystals are discussed with reference to known models. The dispersion curves of diamond have been computed on the basis of the shell model of Cochran applicable to covalent crystals. Parameters have been determined using elastic constants and dispersion curves along the Δ and A directions from the neutron spectrometric data of Warren et al. In general there is good agreement between the calculated curves and experiment. The average error is about 4.8%. Although the calculated curves seem to be a definite improvement over the curves calculated by Smith there appears to be a certain discrepancy between theory and experiment. Plausible causes of this discrepancy are pointed out. 相似文献
9.
10.
Ab initio calculations of the elastic, electronic, optical, and vibrational properties of PdGa compound under pressure
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The structural, elastic, electronic, optical, and vibrational properties of cubic PdGa compound are investigated using the norm-conserving pseudopotentials within the local density approximation (LDA) in the framework of the density functional theory. The calculated lattice constant has been compared with the experimental value and has been found to be in good agreement with experimental data. The obtained electronic band structures show that PdGa compound has no band gap. The second-order elastic constants have been calculated, and the other related quantities such as the Young’s modulus, shear modulus, Poisson’s ratio, anisotropy factor, sound velocities, and Debye temperature have also been estimated. Our calculated results of elastic constants show that this compound is mechanically stable. Furthermore, the real and imaginary parts of the dielectric function and the optical constants such as the electron energy-loss function, the optical dielectric constant and the effective number of electrons per unit cell are calculated and presented in the study. The phonon dispersion curves are also derived using the direct method. 相似文献
11.
In the study of integrable systems of ODE's arising from a Lax pair with a parameter, the constants of the motion occur as spectral curves. The specific curves depend upon the representation of the Lie algebra. In this paper a Galois theory of spectral curves is given that classifies the spectral curves from an integrable system. The spectral curves correspond to conjugacy classes of certain subgroups of the Weyl group for the Lie algebra. The theory is illustrated with the periodic Toda lattice.Partially supported by a Louisiana Education Quality Support Fund grant LEQSF (87-89)-RD-A-8 相似文献
12.
Renu Choithrani Mala N. RaoS.L. Chaplot N.K. GaurR.K. Singh 《Journal of magnetism and magnetic materials》2011,323(12):1627-1635
A shell model has been used to study the structure, phonon dynamics and phase coexistence of perovskite manganites RMnO3 (R=Tb, Dy, Ho). The calculated crystal structure, Raman and IR frequencies and specific heats are found to be in good agreement with the available experimental data. The phonon density of states, elastic constants, elastic stiffness, shear constants and phonon dispersion curves have been computed for these manganites. A zone center imaginary Au mode is revealed in these phonon dispersion curves, which indicates the occurrence of the metastability of the perovskite phase. The Gibbs free energy values calculated as a function of temperature and pressure for RMnO3 in the orthorhombic phase, when compared with those of the hexagonal phase, reveal the possibility of coexistence of these two phases in the present multiferroic manganites under ambient conditions. 相似文献
13.
Sylvie Magnier Monique Aubert-Frécon 《Journal of Quantitative Spectroscopy & Radiative Transfer》2003,78(2):217-225
A theoretical study of the electronic structure of K2+ is presented. Potential energy curves for the ground and various electronic excited states have been computed in the framework of a model potential method over a wide range of internuclear distances. Spectroscopic constants for the lowest short-range bound states have been determined and they are compared with available experimental and theoretical values. Long-range structures (wells and humps) have been also predicted, some of which being described from a long-range model. 相似文献
14.
《Infrared physics》1992,33(6):581-582
In the present paper we have calculated the phonon dispersion curves and dielectric constants, their volume derivatives and the Gruneisen parameters of the mixed alkali halide NaCl0.5Br0.5, using the extended three body force shell model. The results of dielectric constants, their volume derivatives and Gruneisen parameters are found to agree reasonably well with the experimental values, which establishes the validity of the three body charge transfer parameter. With this concept the phonon dispersion curves are obtained in all the three symmetry directions (q,o,o), (q,q,o) and (q,q,q), which will be of interest for experimental workers, since no experimental values have so far been obtained for phonon frequencies. 相似文献
15.
16.
The second order pseudopotential theory suggests the possibility of a break-up of the total energy of simple metals into a
purely volume-dependent part and an effective central pairwise interaction between ions. In the present paper finite contributions
for these two parts of the energy have been extracted in a form convenient for calculation. Using the local Heine-Abarenkov
model potential, a reliable effective ion-ion interaction is generated and the volume-dependent energy is calculated for Al.
The relative contributions of the effective interaction and the volume-dependent energy term to various metallic properties
are also calculated. The importance of volume dependence on the effective interaction is also discussed.
The interactomic force constants upto eighth neighbour are derived from the effective interaction and it is found that the
force constants beyond the third neighbour are negligibly small. This result is also confirmed by the calculation of dispersion
curves with force constants obtained from the effective interaction upto the third neighbour which is found to reproduce the
results of the full pseudopotential calculations. The force constants obtained are also used to study some finite temperature
properties of Al in the quasi-harmonic approximation and the limitations of the theory are pointed out. 相似文献
17.
The phonon dispersion curves, phonon frequency distribution function as well as the lattice specific heat of body-centred
tetragonal indium have been deduced using a lattice dynamical model which includes central, angular and volume forces. Six
elastic constants, four zone boundary frequencies and an equilibrium condition were used in the evaluation of the force constants.
It is shown that this model is elastically consistent and satisfies the symmetry requirements of the lattice, the phonon frequencies
of indium deduced from it are in very good agreement with the experimental values of Reichardt and Smith and the theoretical
values of Garrett and Swihart, and theθ
D values compare well with the experimental values over a wide temperature range. The apparent discrepancies in the phonon
dispersion curves and theθ
D-T curves obtained from deficient models, importance of umklapp processes and the significance of angular forces in the lattice
dynamical models are discussed. 相似文献
18.
B. Prevot C. Carabatos C. Schwab B. Hennion F. Moussa 《Solid State Communications》1973,13(10):1725-1727
Phonon dispersion curves of CuBr have been measured at room temperature in the [001], [110] and [111] directions using inelastic neutron scattering. The results are interpreted in terms of a rigid ion model. Estimations are given for elastic constants. 相似文献
19.
Self-consistent band calculations on four intermetallic compounds of the CsCl structure are presented. The calculations were performed employing the self-consistent ultrasoft pseudopotential method based on the density functional theory, within the local density approximation and the generalized gradient approximation. The calculations predicted that the equilibrium lattice constants are in excellent agreement with the experiment for CoAl and are 1% smaller than experimental values for CoBe, CoSc and CoZr, respectively. In the present study, ordered CoAl do not show any magnetic moment, whereas the other three compounds have moderate magnetic moments of about 0.2 and 0.7 Bohr magnetons (μB ) per atom. The elastic constants are calculated using two approaches, the energy-strain method and the use of phonon dispersion curves. The values obtained from the two methods are in reasonable agreement for the studied intermetallic compounds CoZ (Z?=?Al, Be, Sc and Zr). The brittleness and ductility properties of CoZ (Z?=?Al, Be, Sc and Zr) are determined by Poisson’s ratio σ criterion and Pugh’s criterion. The calculated elastic constants satisfy the mechanical stability criterion and the ductility of CoZr and CoSc is predicted by Pugh’s criterion. The band structure and density of states, and phonon dispersion curves have been obtained and compared with the available experimental results as well as with existing theoretical calculations. We studied and discussed the position of Fermi level for the selected four intermetallic compounds. 相似文献
20.
H. Habli H. Ghalla B. Oujia F.X. Gadéa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,64(1):5-19
In the present work, all adiabatic potential energy curves, spectroscopic constants and
dipole moments of CaH+ molecular ion dissociating below the ionic limit
Ca2+H− are presented. These curves are determined by an ab initio
approach involving a non-empirical pseudo-potential for the Ca core, core-valence
correlation accounted in operator form with two types of core polarization potentials
(CPP) and full valence Configuration Interaction. The molecule is thus treated as a
two-electron system. The potential energy curves and the spectroscopic constants are
presented. In addition, the permanent and transition dipole moments are calculated for
most of the states and reveal the underlying ionic states. A rather good agreement with
the available theoretical works in the literature is obtained for the spectroscopic
constants of the lowest states of the CaH+ molecule. 相似文献