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Issue 46, 2015
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Low temperature phase transition induced biaxial negative thermal expansion of 2,4-dinitroanisole

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Abstract

The crystal structure of 2,4-dinitroanisole (24DNAN) is known to have two polymorphic structures (Z′ = 2 and Z′ = 1, hereafter referred to as α-form and β-form, respectively) and the oxygen atoms of the nitro group(s) of both polymorphs have been found to be disordered over two positions at 298 K. In the thermal behaviour studies of 24DNAN, the β-form showed a phase transition at 264.5 K on cooling. To investigate this phase transition variable-temperature single-crystal X-ray diffraction measurements were carried out. The β angle for the β-form dramatically changed from 90.190° (298 K) to 96.716° (100 K). The length of the b axis shows negative thermal expansion, 13.741(5) to 13.810(5) Å (with a change in temperature from 298 K to 100 K). The thermal expansion coefficients along the principal axes X1, X2, and X3 are −31(6), −15(7) and 262(20) MK−1 (261–100 K), respectively. 24DNAN showed an unusual biaxial NTE induced by a low temperature phase transition.

Graphical abstract: Low temperature phase transition induced biaxial negative thermal expansion of 2,4-dinitroanisole

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Publication details

The article was received on 07 Jan 2015, accepted on 08 Jun 2015 and first published on 30 Jun 2015


Article type: Paper
DOI: 10.1039/C5CE00029G
Citation: CrystEngComm, 2015,17, 8888-8896
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    Low temperature phase transition induced biaxial negative thermal expansion of 2,4-dinitroanisole

    H. Takahashi and R. Tamura, CrystEngComm, 2015, 17, 8888
    DOI: 10.1039/C5CE00029G

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