1980
DOI: 10.1039/dc9806900007
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Double-well potentials and structural phase transitions in polyphenyls

Abstract: In their crystalilne phases, the conformation of non-rigid polyphenyl molecules results from a delicate balance between competing intramolecular and intermolecular forces. At low temperature, the polyphenyl crystals undergo structural phase transitions associated with stabilization of a nonplanar conformation, with respect to a torsional angle between the phenyl rings. An interesting feature is the different natures of these phase transitions: displacive in biphenyl and order-disorder in p-terphenyl. In order … Show more

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Cited by 102 publications
(51 citation statements)
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“…While the value of (L 22) in the nearly-planar 4-hydroxybiphenyl is almost twice as large as is observed for several other twisted biphenyl derivatives (see above), it is much smaller than the values of 178 deg 2 and upwards found for the central rings of p-terphenyl and p-quaterphenyl at temperatures above their orderdisorder phase transitions (Cailleau et al, 1980). We therefore conclude that the 4-hydroxybiphenyl molecule in this structure is not affected by any important static disorder.…”
Section: C12han204c 12h100mentioning
confidence: 75%
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“…While the value of (L 22) in the nearly-planar 4-hydroxybiphenyl is almost twice as large as is observed for several other twisted biphenyl derivatives (see above), it is much smaller than the values of 178 deg 2 and upwards found for the central rings of p-terphenyl and p-quaterphenyl at temperatures above their orderdisorder phase transitions (Cailleau et al, 1980). We therefore conclude that the 4-hydroxybiphenyl molecule in this structure is not affected by any important static disorder.…”
Section: C12han204c 12h100mentioning
confidence: 75%
“…That result is not unexpected considering that there is a maximum in the intramolecular energy surface at ~, = 0 °, and a minimum somewhere between 30 and 45°. Presumably the intermolecular energy for this structure has a minimum at ~,--0 °, and the effect of the intramolecular component is either to flatten the bottom of this well or to introduce a central barrier that is small relative to kT (see Cailleau et al, 1980). An approximately equivalent interpretation of the molecular motion for biphenyl itself, which has L 22 = 109 (3) deg 2 at 298 K and ~--0 by symmetry (Charbonneau & Delugeard, 1977), has been given by Busing (1983).…”
Section: C12han204c 12h100mentioning
confidence: 99%
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“…As is now well established (Cailleau, Baudour, Meinnel, Dvorkin, Moussa & Zeyen, 1980;Raich & Bernstein, 1984), the equilibrium conformation of a polyphenyl molecule in the crystal results from a delicate balance between two competing interactions: the intramolecular forces which tend to twist the molecule [the phenyl-phenyl torsion angle is about 4Y ~ in the gaseous biphenyl (Bastiansen, 1949)] and intermolecular forces which tend to make it planar. We assume that for rotation ~o about the long molecular axis (measured from the average molecular plane) each p-terphenyl phenyl ring is subject to harmonic intermolecular forces C,,q~ governed by a single force constant C,,.…”
Section: A Simple Model/or P-terphenylmentioning
confidence: 99%
“…In the low-temperature phase 6a goes to zero, which means that ql = (0,fl,0) is the only basic satellite and therefore d = 1. Hence K = 2/m and the Bravais class is in the setting with unique axis c given by: P2/m(O,O,7) = 1-6 (Cailleau, Baudour, Meinnel, Dworkin, Moussa & Zeyen, 1980;Cailleau, 1981).…”
Section: (C) Thbrmentioning
confidence: 99%