| 释义 |
polytypism|pɒlɪˈtaɪpɪz(ə)m|
[f. polytypic a. + -ism.]
1. [After G. polytypie (H. Baumhauer 1915, in Zeitschr. f. Krist. u. Min. LV. 252).] A kind of polymorphism in which a substance occurs in a number of crystalline modifications (polytypes) which differ only in one of the dimensions of the unit cell.
1944N. W. Thibault in Amer. Mineralogist XXIX. 266 Following Baumhauer, the phenomenon is called ‘polytypism’ the adjective being ‘polytypic’ and each one of the different modifications a ‘type’. 1951Phil. Mag. XLII. 1016 It has long been recognized that the relationship between the various forms of carborundum is so close as to deserve a special name ‘polytypism’. 1973L. Suchow in P. F. Weller Solid State Chem. & Physics I. ii. 130 All compounds exhibiting polytypism are..of the layer-structure type. 1974Verma & Trigundayat in C. N. R. Rao Solid State Chem. ii. 52 The modifications, called polytypes or simply types, differ only in the arrangement of packing of the close-packed planes of the solids... In this sense the polytypism may be termed one⁓dimensional polymorphism, although its origin seems to be distinctly different from the latter.
2. Biol. The occurrence of several variant forms within a single species. Also ˈpolytypy in the same sense.
1949W. F. Albright Archaeol. of Palestine iii. 57 The polytypism now known to be characteristic of early man is equally characteristic of dogs, whose classification as a single species is not disputed by zoologists. 1961G. G. Simpson Princ. Animal Taxon. iv. 135 In cases of extreme polytypy, first consideration should be given to making the taxon less unwieldy by use of intermediate lower taxa or subgroups. |