ISSN:0889-311X    

DOI:10.1080/08893119108032956

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The electron density that is observed by X-ray diffraction differs from the theoretical static density defined via the Born Oppenheimer approximation because of intermolecular interactions in the crystal and vibrational smearing. Also, the experimental deformation density as mapped by difference Fourier synthesis is often biased by the promolecule model used in the derivation of the nuclear parameters. Better models account for the deformation density in parametric form. With the convolution approximation for vibrational smearing, such models permit the mapping of a static deformation density, provided good high-resolution data are used. Results are usually more accurate in a centrosymmetric space group but the center of inversion itself is assumed without direct experimental evidence.

ISSN:0889-311X    

DOI:10.1080/08893119108032957

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

It seems that it might be due to a combination of practical and historical circumstances that the unpolarised neutron diffraction method, applied usually to powder samples, still dominates structure determinations of antiferromagnets. Polarised-beam methods are used for ferromagnets. There is also a more advanced polarised-neutron single-crystal method for antiferromagnets, which is at last beginning to emerge, and this paper outlines the conceptual changes that are involved in adapting to this little-known revision of methodology, for multidomain antiferromagnetic structures. Further analyses are presented of initialUND-FFI-NPA(A)results, for atP3z antiferromagnett1, AuMn for example, and the discussion is extended to the possibilities for further study, such as with a differentUND-FFI-NPA(D)experimental arrangement. By introducing additional techniques to determine the moment directions in individual coherent domains, the studies can proceed to more rigorous and detailed investigations of the form-factors in antiferromagnets of various symmetries. Some appropriate form-factor expressions are presented.

ISSN:0889-311X    

DOI:10.1080/08893119108032958

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0889-311X    

DOI:10.1080/08893119108032955

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor