Space-group frequencies for organic compounds

Mighell, A. D.; Himes, V. L.; Rodgers, Jayne

doi:10.1107/s0108767383001464

Cited by 127 publications

(61 citation statements)

References 2 publications

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“…The distribution is shown in (Table 2). As observed earlier (Mighell, Himes & Rodgers, 1983), about 78% of the compounds were described in only five space groups. The distribution of compounds among the seven crystal systems (Table 3) shows that, for those structures with more than one formula unit in the asymmetric unit, there is about a 1-8-fold increase in the population of the triclinic system, whereas in the orthorhombic system the population decreased by about 1.5-fold when compared with the distribution for all crystal structures listed in the database.…”

mentioning

confidence: 57%

“…These errors are due to compounds reported in (1) incorrect space group but correct crystal system, (2) incorrect space group and incorrect crystal system (Mighell, Himes & Rodgers, 1983). The unequivocal space-group determination of the given crystal structure can only be through the least-squares refinement of the structure in various candidate space groups and distinguishing between them through significance tests (Hamilton, 1964).…”

Section: Discussionmentioning

confidence: 99%

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Space-group frequencies of proteins and of organic compounds with more than one formula unit in the asymmetric unit

Natarajan¹,

Ramakumar²,

Viswamitra³

1990

Acta Cryst Sect A

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P. J. BAKER et al. 725resolution increases. Therefore, the anomalous-scattering signal is clearly better for the short-wavelength data rather than the longer-wavelength data. Furthermore, the ratio of w" /w" where is the ~t ncalc/J--, , FHcalc anomalous contribution of the anomalous-scattering atoms to the structure factor and E" is the r.m.s, lack of closure for the anomalous case, as a function of resolution (Fig. 4) is greater, on average by a factor of two, for the EMP derivative and this pattern is extended to the F,L~ R factor (47.1% EMP; 51.0% DBMMF) and the overall figure of merit for the resultant phase set (0.58 EMP; 0.51 DBMMF). These results indicate that, for these two very similar derivatives, the anomalous-scattering signal to noise has been enhanced for the EMP data set, for which the wavelength was chosen to illuminate the LII absorption edge of the Hg atom in conjunction with a reduction in the overall protein crystal absorption at 0.86/~. On PX9.6 it is easy to move between the absorption edges of commonly used heavy ions, such as mercury, platinum and gold, so that MIROAS is routinely useable. The results from this present study with SIROAS illustrate the ease and effectiveness of the procedure. The two benefits of reduced absorption and increased anomalous-scattering signal have increased the phasing power of the EMP derivative of GDH and hence improved the quality of the resultant GDH electron density maps.We thank the SERC for their financial support of this work and for use of the SRS. We also thank J. M. A. Smith for helping to set up station PX9.6 and for subsequent consultations and also all the support staff at Daresbury. DWR is a Lister Institute Research Fellow. AbstractAn analysis of the distribution of organic crystal structures with more than one formula unit in the asymmetric unit among the 230 space groups has been carried out for the compounds listed in the Cambridge

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mentioning

confidence: 57%

Section: Discussionmentioning

confidence: 99%

Space-group frequencies of proteins and of organic compounds with more than one formula unit in the asymmetric unit

Natarajan¹,

Ramakumar²,

Viswamitra³

1990

Acta Cryst Sect A

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“…Kitaigorodsky's hypothesis has been verified experimentally. Of 29059 organic compounds whose crystal structures were determined prior to 1981, 75% crystallized in only five space groups (Mighell, Himes & Rodgers, 1983). These five space groups exhibit combinations of inversion centers, screw axes and/or glide planes which facilitate close-packing in all three lattice directions.…”

Section: Methodsmentioning

confidence: 99%

Predicting the crystal structure of organic molecular materials

Chaka

Zaniewski²,

Youngs³

et al. 1996

Acta Crystallogr Sect B

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This paper describes a novel method for predicting the crystal structure of organic molecular materials which employs a series of successive approximations to focus on structures of high probability, without resorting to a brute force search and energy minimization of all possible structures. The problem of multiple local minima is overcome by assuming that the crystal structure is closely packed, thereby eliminating 217 of the 230 possible space groups. Configurations within the 13 remaining space groups are searched by rotating the reference molecule about Cartesian axes in rotational increments of 15 ° . Initial energy minimization is performed using (6-12) Lennard-Jones pair potentials to produce a set of closely packed structures. The structures are then refined with the introduction of a Coulombic potential calculated using molecular multipole moments. This method has successfully located local minima which correspond to the observed crystal structures of several saturated and unsaturated hydrocarbons with no a priori information provided. For large polycyclic aromatic hydrocarbons, additional refinements of the energy calculations are required to distinguish the experimental structure from a small number of closely packed structures. Our methodology for a priori crystal structure prediction represents the most efficient algorithm presented to date, in a field where the first successes have only been described within the past year and have been few and far between. Since our algorithm is capable of locating a large number of reasonable structures with similar energy in a short period of time, and is more likely to locate a minimum corresponding to the experimental structure, our program provides a superior framework to determine the level of theory required to calculate the intermolecular potential. For all but highly asymmetric hydrocarbons, however, distinguishing the observed structure from a large number of highly probable structures requires more rigorously calculated intermolecular interactions than pair potentials, plus an ad hoc electrostatic potential, and is thus beyond the scope of this paper. All calculations 1" Current address: The

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“…(viii) It has been observed that some space group symmetries are much more common than others in crystals formed from small organic molecules [16,17,18]. Inorganic systems show different space group frequencies [19,20].…”

Section: Potential Energy Surfaces and The Global Searching Problemmentioning

confidence: 99%

Ab initiorandom structure searching

Pickard

Needs²

2011

J. Phys.: Condens. Matter

1,119

989

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Abstract. It is essential to know the arrangement of the atoms in a material in order to compute and understand its properties. Searching for stable structures of materials using first-principles electronic structure methods, such as density functional theory (DFT), is a rapidly growing field. Here we describe our simple, elegant and powerful approach to searching for structures with DFT which we call ab initio random structure searching (AIRSS). Applications to discovering structures of solids, point defects, surfaces, and clusters are reviewed. New results for iron clusters on graphene, silicon clusters, polymeric nitrogen, hydrogen-rich lithium hydrides, and boron are presented.

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Space-group frequencies for organic compounds

Abstract: The space-group frequency for approximately 30 000 organic compounds in the NBS Crystal Data Identification File has been calculated for each of the 230 space groups.

Cited by 127 publications

References 2 publications

Space-group frequencies of proteins and of organic compounds with more than one formula unit in the asymmetric unit

Space-group frequencies of proteins and of organic compounds with more than one formula unit in the asymmetric unit

Predicting the crystal structure of organic molecular materials

Ab initiorandom structure searching

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