ISSN:
1600-5724
Quelle:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Thema:
Chemie und Pharmazie
,
Geologie und Paläontologie
,
Physik
Notizen:
It is shown that it is reasonable to describe some structures such as γ brass and α- and β-Mn completely in terms of tetrahedral configurations of the atoms, even though constraints of the structural geometry do not uniquely prescribe the selected tetrahedra as they do for example in the Laves phases and the β-W structure. Such descriptions use a freedom of choice of tetrahedra in addition to the accepted distortion of tetrahedra in approximating to the non-attainable ideal of filling space with regular tetrahedra. An error parameter is developed which allows comparison of the average distortions of all of the tetrahedra for structures described in terms of tetrahedral configurations of the atoms. Comparison of the error parameters for the γ brasses Cu5Cd8 and Fe3Zn10 and for other structures such as α- and β-Mn where there is freedom of choice in the selection of tetrahedral configurations, with error parameters for other structures such as Cu2Mg and β-W where the tetrahedra are uniquely prescribed by the structural geometry, indicates that the first group of structures can reasonably be regarded as tetrahedral configurations of atoms, although slightly less effectively so than the Cu2Mg and β-W structures. Other γ brasses such as Cu5Zn8 and Cu9Al4 are found to be poorer examples of structures possessing overall tetrahedral configurations.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1107/S0567739475000472
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