Properties of Crystalline Organic Molecules

Day, Graeme M.; Price, Sarah L.

doi:10.1016/b978-012445760-7/50053-8

Cited by 6 publications

(9 citation statements)

References 122 publications

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“…The figure also reveals that relatively few measurements of this kind have been undertaken over the last decade. As previously noted by Day and Price, [60] the breakdown of measured elastic constants into crystal systems differs markedly from that for crystal structures in the CSD (Table 1). In particular, there is a far greater proportion of elastic tensor measurements for high‐symmetry crystals, and only a single measurement (malonic acid [39] ) for a triclinic crystal, a crystal system that comprises 26 % of all crystal structures in the CSD.…”

Section: Introductionmentioning

confidence: 62%

“…Figure 1p lots the cumulative number of experimental determinations of complete tensors against the year in which they were published, spanning ap eriod of the last 61 years.T he trend issurprisingly-closely linear, apart from the abrupt jump in 2001 arising from the large number of measurements reported that year by Siegfried Haussühl. [39] Thefigure also reveals that relatively few measurements of this kind have been undertaken over the last decade.A sp reviously noted by Day and Price, [60] the breakdown of measured elastic constants into crystal systems differs markedly from that for crystal structures in the CSD (Table 1). In particular,there is afar greater proportion of elastic tensor measurements for high-symmetry crystals,and only asingle measurement (malonic acid [39] )for at riclinic crystal, ac rystal system that comprises 26 %o fa ll crystal structures in the CSD.T his skewing of measurements away from low-symmetry systems is almost certainly ac onsequence of the greater number of independent elastic constants that need to be determined (Table 1) and the subsequent measurements along different crystal directions required for their determination.…”

Section: Overview Of Experimental Measurementsmentioning

confidence: 85%

“…Twenty years ago, Day and Price [60] summarised the experimental measurements of elastic constants of organic crystals at that time in terms of two plots: a cumulative plot of measurements over time, as well as a comparison of the distribution of those crystal systems with that for organic materials in the Cambridge Structural Database (CSD). Here we update both of those comparisons, but with a slightly different emphasis.…”

Section: Introductionmentioning

confidence: 99%

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Quantifying Mechanical Properties of Molecular Crystals: A Critical Overview of Experimental Elastic Tensors

et al. 2021

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This review presents a critical and comprehensive overview of current experimental measurements of complete elastic constant tensors for molecular crystals. For a large fraction of these molecular crystals, detailed comparisons are made with elastic tensors obtained using the corrected small basis set Hartree–Fock method S‐HF‐3c, and these are shown to be competitive with many of those obtained from more sophisticated density functional theory plus dispersion (DFT‐D) approaches. These detailed comparisons between S‐HF‐3c, experimental and DFT‐D computed tensors make use of a novel rotation‐invariant spherical harmonic description of the Young's modulus, and identify outliers among sets of independent experimental results. The result is a curated database of experimental elastic tensors for molecular crystals, which we hope will stimulate more extensive use of elastic tensor information—experimental and computational—in studies aimed at correlating mechanical properties of molecular crystals with their underlying crystal structure.

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Section: Introductionmentioning

confidence: 62%

Section: Overview Of Experimental Measurementsmentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

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Quantifying Mechanical Properties of Molecular Crystals: A Critical Overview of Experimental Elastic Tensors

et al. 2021

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“…[7][8][9][10][11] Unlike metallic, covalent, and ionic crystals, there is a scarcity of experimentally determined elastic constants for molecular organic crystals. 12 This is a consequence of difficulties in growing crystals of adequate size and quality, the predominance of low-symmetry space groups of molecular crystals (which increases the number of independent elastic constants to be determined), and measurement problems resulting from the relative softness of intermolecular interactions. There is, there-fore, a need to develop and assess computational methods for predicting elastic constants of such crystals.…”

Section: Introductionmentioning

confidence: 99%

Elastic Constant Calculations for Molecular Organic Crystals

Day

Price

Leslie

2000

Crystal Growth & Design

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109

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Elastic constants of a set of molecular organic crystals have been calculated within the crystal modeling program DMAREL, which was developed to allow the use of highly accurate, anisotropic atom-atom potentials. A set of six molecular crystals (durene, m-dinitrobenzene, the form of resorcinol, pentaerythritol, urea, and hexamethylenetetramine) has been chosen to sample a range of intermolecular interactions and crystal symmetries. The sensitivity of such calculations to variations in empirical repulsion-dispersion parameters and the electrostatic model is determined and discussed relative to the other errors in the theoretical model and typical experimental uncertainties. We find that model potentials whose functional form has been simplified often reproduce crystal structures and lattice energies adequately but perform poorly when used to calculate elastic constants. This is because more theoretically justified potentials are required to satisfactorily model the curvature at the equilibrium geometries. The rigid-molecule approximation can result in exaggerated elastic constants, and the neglect of thermal effects also leads to significant overestimation of the stiffness constants.

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“…The estimated elastic constants for all three forms are provided in the Supporting Information, as industrially useful for process modeling. The other structures, including the sheet structures, all had reasonable mechanical properties for organic crystals, though the anisotropy in the elastic tensor reflected the packing.…”

Section: Resultsmentioning

confidence: 99%

Characterization of Complicated New Polymorphs of Chlorothalonil by X-ray Diffraction and Computer Crystal Structure Prediction

et al. 2004

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A simultaneous experimental and computational search for polymorphs of chlorothalonil (2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile) has been conducted, leading to the first characterization of forms 2 and 3. The crystal structure prediction study, using a specifically developed anisotropic atom-atom potential for chlorothalonil, gave as the global minimum in the lattice energy a structure that was readily refined against powder diffraction data to the known form 1 (P2(1)/a). The structure of form 2 was solved and refined from powder diffraction data, giving a disordered structure in the Rm (166) space group (Z = 3). It could also be refined against a P1 ordered model, starting from a low-energy hypothetical sheet structure found in the computational search. This shows that the disorder could be associated with the stacking of ordered sheets. The disordered structure for form 2 was later confirmed by single-crystal X-ray diffraction. The structure of form 3, determined from single-crystal diffraction, contains three independent molecules in the asymmetric unit in P2(1) (4) (Z = 6). Powder diffraction showed that this single-herringbone structure was similar to two low-energy structures found in the search. Further analysis confirmed that form 3 has a similar lattice energy and contains elements from both these predicted structures, which can be considered as good approximations to the form 3 structure.

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Properties of Crystalline Organic Molecules

Cited by 6 publications

References 122 publications

Quantifying Mechanical Properties of Molecular Crystals: A Critical Overview of Experimental Elastic Tensors

Quantifying Mechanical Properties of Molecular Crystals: A Critical Overview of Experimental Elastic Tensors

Elastic Constant Calculations for Molecular Organic Crystals

Characterization of Complicated New Polymorphs of Chlorothalonil by X-ray Diffraction and Computer Crystal Structure Prediction

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