14214 IUPAC Gold Book - rod group 10.1351/goldbook.14214 14214 current synonym: line repetition group 1 Symmetry group of a three-dimensional array of atoms, regularly repeating along one direction. The symmetry of isolated polymer chains, with translational periodicity along the chain axis direction, may be described by either the rod group, or the equivalent line-repetition-group approach. Whereas the line-repetition-group description has been developed in the polymer science community, rod groups originate in the crystallographic community and are more systematic. Table 1 shows the symmetry group symbols of some linear polymers according to both the rod-group and the line-repetitiongroup description. Details concerning the symbols used are explained in crystallographic literature can be found in the recommendation. For reasons related to space filling, in the case of crystallographic rod groups, only two-, three-, four-, and sixfold screw axes are taken into consideration. Such limitations do not exist in the case of isolated chains for which any helical symmetry may, in principle, be acceptable. In other words, rod groups in are a subset of those applicable to ideal crystalline chain conformations. The examples given in Table 1 pertain to linear polymers and apply to ideal crystalline chain conformations, whereas the crystallographic symmetry of the chain in the crystal is often lower, i.e., some symmetry elements applicable to the ideal crystalline chain conformation do not apply to the crystalline packing. ideal crystalline chain conformations https://goldbook.iupac.org//terms/view/14210 PAC, 2011, 83, 1831. 'Definitions of terms relating to crystalline polymers (IUPAC Recommendations 2011)' on page 1842 (https://doi.org/10.1351/PAC-REC-10-11-13) https://goldbook.iupac.org/terms/view/14214/html https://goldbook.iupac.org/terms/view/14214/json https://goldbook.iupac.org/terms/view/14214/plain Citation: 'rod group' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.14214 The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using. 2026-08-09T06:15:33+00:00