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Second‐order quadrupole shift in the incommensurate structures of Rb 2 ZnBr 4 and Rb 2 ZnCl 4
Author(s) -
Aleksandrova I. P.,
Grande S.,
Moskvich Yu. N.,
Krieger A. I.,
Koptsik V. A.
Publication year - 1983
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221150232
Subject(s) - tensor (intrinsic definition) , symmetry (geometry) , quadrupole , order (exchange) , physics , condensed matter physics , chemistry , phase transition , zero (linguistics) , crystallography , quantum mechanics , mathematics , linguistics , philosophy , geometry , finance , pure mathematics , economics
The angular dependences of second‐order 87 Rb (1/2 → −1/2) shift in the incommensurate phases of Rb 2 ZnBr 4 and Rb 2 ZnCl 4 are interpreted and EFG‐tensors at the special points of the displacement profile are determined. The EFG‐tensor of I‐structure is described in the approach of perturbance theory: V ij { S } = V ij 0 { S } + Δ V ij n { S } where the EFG‐tensor of the paraelectric phase is taken as zero‐approximation. It is most important that the form of “modulation correction” tensor Δ V ij is not arbitrary. The symmetry properties of one‐dimensional incommensurate modulated atomic chain determine the selection rule for the non‐zero components of the tensor of modulation corrections. The existence of supersymmetry for structurally incommensurate systems follows from the presented NMR‐experiments. The abstract symmetry conservation law at commensurate‐incommensurate transition seems to be demonstrated in this experiment.