Solids modelled by crystal field <i>ab initio</i> methods. 5. The phase transitions in biphenyl from a molecular point of view

Lenstra, A. T. H.; Alsenoy, C. Van; Verhulst, K.; Geise, H. J.

doi:10.1107/s0108768193007931

Cited by 36 publications

(32 citation statements)

References 20 publications

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“…Theoretical model calculations for several oligophenylenes on different levels reproduced and verified the experimental results (see e.g. [45,52,58,62]). On the other hand, the other part of the investigated molecules is represented by the diphenyl-1,3,4-oxadiazole moiety.…”

Section: Tablesupporting

confidence: 61%

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Ordering the amorphous – Structures in PBD LED materials

Emmerling

Orgzall

Dietzel

et al. 2012

Journal of Molecular Structure

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Section: Tablesupporting

confidence: 61%

“…The results indicate at least three different phases [58]. The monoclinic structure P2 1 /a is observed from ambient conditions down to 40 K where a transition to another monoclinic structure (space group Pa) occurs due to changes of the molecular conformation.…”

Section: Tablementioning

confidence: 91%

Ordering the amorphous – Structures in PBD LED materials

Emmerling

Orgzall

Dietzel

et al. 2012

Journal of Molecular Structure

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“…Phase transitions that occur during cooling and that are associated with an integral multiplication of the cell volume are no surprise; classic examples are biphenyl (Baudour, 1991;Lenstra et al, 1994, and references therein) and ferrocene (Seller & Dunitz, 1979;Dunitz, 1993). These transitions are often the result of a`short' atom±atom contact that is acceptable when the temperature is higher and the vibrational amplitudes larger, but that becomes increasingly unfavorable as the vibration amplitudes decrease (see Busing, 1983).…”

mentioning

confidence: 99%

Two fluoradene derivatives: pseudosymmetry, eccentric ellipsoids and a phase transition

Xia

Selegue

Carrillo

et al. 2001

Acta Crystallogr Sect B

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Structures of two derivatives of the curved¯uoradene ring system (C 19 H 12 ) have been determined. Both have phases that are highly pseudosymmetric. At room temperature crystals of 7b-triisopropylsilyl¯uoradene (C 28 H 32 Si) have a P " 1 cell that contains two independent molecules (Z = 2) and that is almost centered. Crystals of 7b-(2,4-dinitrophenyl)¯uoradene (C 25 H 14 N 2 O 4 ) have both a P2 1 /c cell with Z = 1 and a P2 1 /c cell with Z = 2. The molecular volumes in these two P2 1 /c structures differ by 0.7%, but the structures are otherwise virtually the same; the two independent molecules in the larger cell are related by a pseudotranslation. Some of the atomic ellipsoids in the P2 1 /c, Z = 1 structure are very large and eccentric, and there are some hints in the diffraction pattern of an incipient phase transition, but the Z = 1 and Z = 2 phases are clearly different. The P2 1 /c, Z = 2 crystal at 295 K probably contains some volume fraction of the Z = 1 phase; when the temperature is lowered to 273 K this fraction is decreased markedly. The pronounced pseudosymmetry in the P " 1 and P2 1 /c structures that have Z = 2 has been investigated by analysing the atomic coordinates, by performing re®ne-ments in the smaller pseudocells and by making separate Wilson plots for the classes of re¯ections which are systematically strong and systematically weak. All three approaches are informative, but they reveal different information. Leastsquares ®ts of coordinates of corresponding atoms measure the similarity of the molecular conformations. The Wilson plots allow a quantitative comparison of the intensities of the strong and weak re¯ections and thus an assessment of the deviations of the true structure from the smaller pseudocell structure. Comparison of the atomic displacements obtained in the full and pseudocell re®nements shows where the structural distortions are largest and provides an indication of their directions."

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“…In [59] the planar conformation of the molecule was interpreted as the result of dynamic disorder with hfi time ¼ 0 and an actual molecular equilibrium geometry of f ¼ 27 (but please note, that also in this description the crystal packing with its intermolecular forces has a flattening effect on the individual molecules). At low temperatures two modulated crystalline phases with non-planar molecules (f 6 ¼ 0 ) [56,60,61] in the crystal structure are found.…”

Section: Even a H--h Distance Of D H--h ¼ 22 å Is Reportedmentioning

confidence: 99%

Organic molecular compounds with modulated crystal structures

Schoenleber¹

2011

Zeitschrift Für Kristallographie

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Abstract. Even though the higher-dimensional superspace approach is an established method to describe aperiodic crystal structures, it is not yet fully considered and applied by a larger community of scientists. In this contribution the structural description of incommensurately and commensurately modulated molecular compounds is discussed and it is shown, that the higher-dimensional superspace approach is an elegant way for an exact structural description and an exact crystal-chemical analysis of such structures. While discussing several modulated molecular compounds, the idea behind the higher-dimensional superspace approach is shown. On the examples treated in the discussion it is explained, how to understand and how to interprete modulated molecular compounds. Also a short introduction is given to the higher-dimensional superspace approach itself, to the basic principles and to the applied nomenclature.

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Solids modelled by crystal field ab initio methods. 5. The phase transitions in biphenyl from a molecular point of view

Abstract: Using ab &itio calculations at the 4-21G level and procedures for extrapolation to rg geometry as well as using the electrostatic crystal field (ECF-MO) approach, the geometry and torsion potential were calculated for 1,1'-biphenyl in the gas phase, in the

Cited by 36 publications

References 20 publications

Ordering the amorphous – Structures in PBD LED materials

Ordering the amorphous – Structures in PBD LED materials

Two fluoradene derivatives: pseudosymmetry, eccentric ellipsoids and a phase transition

Organic molecular compounds with modulated crystal structures

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