摘要:

AbstractA dynamical theory is developed of the Mossbauer radiation diffraction by crystals being subjected to an variable external field action. Equations describing the dynamical diffraction by nonstationary crystals are obtained. It is shown that the resonant interaction between Mössbauer radiation and shift field induced in the crystal by a variable external field giving rise to an effective conversion of the incident wave into a wave with changed frequency

ISSN:0370-1972    

DOI:10.1002/pssb.2221330109

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractA calculation of the implicit shift to the phonon energies for phonons in deuterated naphthalene atq=0is presented, the “explicit shift” having been already described in an earlier paper. With this the calculation of the shift in the phonon energies due to temperature becomes complete and consistent, ready for direct comparison with the measured results of the shift obtained by neutron scattering experiments. The results for the total calculated shift in the phonon energies, arising from both, the explicit anharmonic terms and the implicit (i.e. the volume dependent) shift are presented and compared with the experimental neutron scattering results. The calculations of thermal expansion, compressibility, and the Grüneisen constants which naturally enter the calculation of the implicit shift, are also described and a comparison with the experimental neutron scattering results of these also is made. All the results are very satisfactory, strengthening the faith in the assumption for the model of the molecular crys

ISSN:0370-1972    

DOI:10.1002/pssb.2221330110

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractA simple theory is developed to study the pressure dependence of Grüneisen parameter, γ. The final results show that γ varies linearly with the pressure, that is, γ(p,T) = γ(0,T) – ηpwhere η is found to be a pressure‐independent but temperature‐dependent parameter. Moreover, it is shown that η is related to some other thermodynamic parameters and hence can have positive or negative magnitude which in turn will decide whether γ(p,T) decreases or increases with pressure. The calculated values of γ(p,T) in the whole range of pressure and temperature are found in very good agreement with the experimental results in case of all the solids studied like NaCl, CaF2, MgO, quartz, Na, K, and Li. Further, it is shown that the second Grüneisen parameter,q, and the Debye temperature, θ, can also be calculated as a function of pressure with the help of t

ISSN:0370-1972    

DOI:10.1002/pssb.2221330111

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractEnergy thresholds of splitting displacement cascades into subcascades are calculated for some materials on the basis of the theory developed earlier. The group representation of splitting is constructed and the density of subcascade size distribution is obtained. A simple method for analytical estimation of temperature influence on splitting is suggested.

ISSN:0370-1972    

DOI:10.1002/pssb.2221330112

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe windforce acting upon a host atom and the impurities Ta, Cr, and Ni in niobium is calculated in a finite cluster model. In this model all strong and multiple scattering effects up tolmax= 2 are preserved. Special attention is given to the influence of the vacancy, the cluster size, and of charge transfer. A positive windforce is found, in accordance with experiment, so that this appears to be not directly related to a hole current contribution, contrary to what is believed commonly.

ISSN:0370-1972    

DOI:10.1002/pssb.2221330113

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractA system of equations is derived for the evolution under action of cross‐relaxation (CR) of the dipole–dipole reservoir (DDR) and Zeeman subsystems, redefined taking into account the fact, that the part of secular dipole‐dipole interactionH′d, which causes homogeneous displacement of spin resonant frequencies at low temperatures (LT) must be subtracted fromH′d. The case is considered, when the influence of the change of LT displacement due to CR on the energy, absorbed by DDR, is stronger, than that of the usual high‐temperature term. It is shown, that in this situation both, DDR and spins under CR acquire a negative temperature in spite of the fact, that the frequency of saturated spins is smaller than the frequency of spins under CR. This behaviour differs from the high‐tempe

ISSN:0370-1972    

DOI:10.1002/pssb.2221330114

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe charge electrostatic energy W(z) near the surface of a metal with an arbitrary spontaneous magnetization 0 ≦ ζ ≦ 1 is calculated using the random‐phase approximation for the metal dielectric function. It is shown that the variation of the surface valueW(0) under the ferromagnetic transition amounts up to 12% of its original value and depends on free‐electron concentration. Such a variation can be observed in LEED exp

ISSN:0370-1972    

DOI:10.1002/pssb.2221330115

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe ground state phase diagram of the extended Hubbard model for arbitrary electron density is investigated with the broken‐symmetry Hartree approximation. It is found that for two‐sublattice orderings, only the charge‐order and the antiferromagnetism exist without the mixed

ISSN:0370-1972    

DOI:10.1002/pssb.2221330116

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractA detailed SCCF calculation of the magnon densities of states of 1‐D binary alloys, both with statistical short range order and purely random ones, is presented and the results are compared with the electronic densities of states of those alloys. Also the demonstration of the higher spatial correlations (HSC) in the shapes of the magnon densities of states is discussed. It is shown that for some constitutions of 1‐D binary alloys the long range magnetic order is likely to exist and results for the temperature dependence of the magnetization of those binary alloys is also gi

ISSN:0370-1972    

DOI:10.1002/pssb.2221330117

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY

摘要:

AbstractThe effect of a cubic crystal field on rare‐earth ions is calculated and presented in a graphical form representing the individual magnetic moment and Van Vleck susceptibility of the lowest‐lying sub‐state, forJ= 3.5; 4; 4.5; 6; 7.5; 8. This is a practical guide for analyzing the moderate‐field part of the magnetization. The results are given for the three principal directions. In order to analyze susceptibility measurements, the calculated Curie constant (or the Van Vleck susceptibility) of the fundamental multiplet is also repr

ISSN:0370-1972    

DOI:10.1002/pssb.2221330118

出版商:WILEY‐VCH Verlag    

年代:1986

数据来源: WILEY