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Optical evidence of grown‐in strain in solution‐grown hexamethylenetetramine
Author(s) -
Razzetti C.,
Ponzoni A.,
Migi G.,
Zha M.,
Zanotti L.,
Paorici C.
Publication year - 2005
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/crat.200410491
Subject(s) - birefringence , strain (injury) , hexamethylenetetramine , chemistry , analytical chemistry (journal) , optics , materials science , crystallography , organic chemistry , physics , medicine
We report evidence of grown‐in inhomogeneous strain affecting hexa methylene tetramine (HMT) crystals grown from ethanol‐water solution. Irrespective of the excellent optical quality displayed by the samples during growth, as evaluated in‐situ by optical transmission methods, azimuth‐retardation maps of the specimens, tracked by an ad‐hoc developed polarimetric technique, show that the crystals are affected by strain‐induced inhomogeneous birefringence. This feature may provide a rationale to the erratic estimates of the electro‐optical coefficient of HMT reported in literature. We conjecture that this birefringence may originate jointly from the thermo‐elastic effect and the softness of the material, and then that it may be intrinsic to hydrogen‐ and Van der Waals‐ bonded crystals, even if grown at low temperatures. Were this true, it could justify the inhomogeneous strain indirectly observed in a variety of organic compounds. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)