ISSN:0370-1972    

DOI:10.1002/pssb.2221960129

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractCharge transfer in GaAs is analysed utilising our earlier precise and extensive X‐ray diffraction data. The h + k + l = 4n+ 2 structure factors are weak, “quasi‐forbidden” with the constituent atoms of nearly equal but opposite scattering. The measured structure factors are all systematically larger than their calculated values over the entire range of sin θ/λ up to about 10 nm−1. Moreover, they exhibit non‐equivalence of inversereflections with non‐zero indices which can arise only from bonding distortion or anharmonicity. A model calculation for the charge transfer inbonding from the III to the V atom, described by a single parameter x, valid over the entire reciprocal space, is proposed and found to yield a precise estimate for x, namely 0.52(0.12) for GaAs (in electron units). This result is in good agreement with the earlier models, and indicates an appreciable core contribution to the

ISSN:0370-1972    

DOI:10.1002/pssb.2221960102

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

ISSN:0370-1972    

DOI:10.1002/pssb.2221960130

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe effective atomic charges for all sites of the RBa2Cu3O7lattices have been found using our Mössbauer data withthe67Cu(67Zn),133Ba(133Cs),155Eu(155Gd) isotopes, our calculations of the lattice electric field gradient (EFG) at the lattice sites, as well as the17O NMR data available in literature. The charges show holes placed in the chain oxygen sublattice mainly. The Cu2+Sternheimer factor has been estimated and the Cu2+valence EFG in YBa2Cu37has been found. The z‐axes of the total, lattice, and valence EFG tensors for Cu(2) coincide with the crystal axis c. For Cu(1) they coincide with the axes b, a, and a, respective

ISSN:0370-1972    

DOI:10.1002/pssb.2221960103

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe local order around the yttrium atoms in a series of samples belonging to the Y2O3−Al2O3system have been characterised by X‐ray absorption at the yttrium K‐edge. Three types of Y‐O bonds were found in the first coordination shell for samples rich in Y2O3. The garnet‐like aluminates have been elaborated by an original solution‐polyacrylamide ge

ISSN:0370-1972    

DOI:10.1002/pssb.2221960104

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe stress‐strain hysteresis curves of BiVO4single crystals have been studied by thermal mechanical analysis in the ferroelastic and paraelastic phases. The phase transition temperatures are obtained as afunction of stress at various temperatures. The phase transition temperature is found to decrease as the stress is increased. The experimental resultsindicate that the phase transition temperature of the ferroelastic BiVO4shifts to the lower temperature side under the influence of externalstres

ISSN:0370-1972    

DOI:10.1002/pssb.2221960105

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe temperature and pressure dependences of elastic coherent and inelastic incoherent neutron scattering spectra in polycrystalline 1,3‐cyclohexanedione undergoing a first‐order phase transition at 287 K, have been measured. The information on the crystal lattice parameters and thegeneralized phonon density function G(E) is analyzed. The presence of the transition hysteresis and the isomorphous phase transition have been confir

ISSN:0370-1972    

DOI:10.1002/pssb.2221960106

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe kinetics of cluster growth in segregation and crystallization processes in highly viscous materials taking into account stress development andstress relaxation is investigated theoretically. Different models of stressdevelopment are considered for the case that stresses arise due to the formation and growth of the newly evolving phase. The theory is formulated in terms of differential equations describing the evolution of the cluster size, the change in time of the thermodynamic driving force of cluster growth and other related quantities. Based on the numerical solution of these equations several effects are analyzed which may occur as the result of stress development and stress relaxation.

ISSN:0370-1972    

DOI:10.1002/pssb.2221960107

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractWe present a method for the approximate semianalytical calculation of wave functions and eigenenergies in systems consisting of domains with knownbulk solutions of the corresponding Schrödinger equation (e.g. with piecewise constant potential). The trial wave function is written as a normalized linear combination of several bulk solutions for the given energy. The coefficients of the linear combination are found by minimization of the integral of square mismatch along the boundaries. Mathematically the problem is equivalent to the minimization of the Rayleigh quotient or solution of the generalized eigenproblem for the vector of coefficients. The value of the residual provides an estimation of the accuracy of the results and gives thepossibility to choose an optimal set of trial functions. We illustrate the use of the method by calculation of eigenfunctions of infinitely long triangular and quadrilateral wires

ISSN:0370-1972    

DOI:10.1002/pssb.2221960108

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractWe have investigated the possible water adsorption forms on the stepped Si(110) surface. Calculations have been performed by using the empirical tight‐binding method. Two types of adsorption model of water on a single layer stepped Si(110) surface have been considered, one of them is the dissociative type (H, OH) and the other one is the molecular type (H2O). The total electronic energy and TDOS calculations lead to a dissociative type of water adsorption on the stepped Si(110) surface excluding the molecular type as it was found on the flat Si(110) surfac

ISSN:0370-1972    

DOI:10.1002/pssb.2221960109

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY