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Hardness Alternation in α,ω‐Alkanedicarboxylic Acids
Author(s) -
Mishra Manish Kumar,
Ramamurty Upadrasta,
Desiraju Gautam R.
Publication year - 2015
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201500322
Subject(s) - nanoindentation , alternation (linguistics) , indentation , materials science , crystallography , composite material , shear (geology) , deformation (meteorology) , molecular dynamics , chemical physics , chemistry , computational chemistry , philosophy , linguistics
The variation of hardness as a function of the number of carbon atoms in α, ω ‐alkanedicarboxylic acids, C N H 2 N −2 O 4 (4≤ N ≤9), was examined by recourse to nanoindentation on the major faces of single crystals. Hardness exhibits odd–even alternation, with the odd acids being softer and the even ones harder; the differences decrease with increasing chain length. These variations are similar to those seen for other mechanical, physical, and thermal properties of these diacids. The softness of odd acids is rationalized due to strained molecular conformations in them, which facilitate easier plastic deformation. Relationships between structural features, such as interplanar spacing, interlayer separation distance, molecular chain length, and signatures of the nanoindentation responses, namely, discrete displacement bursts, were also examined. Shear sliding of molecular layers past each other during indentation is key to the mechanism for plastic deformation in these organic crystals.