A robust tangent procedure.
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| Title: | A robust tangent procedure. |
|---|---|
| Authors: | Burla, M. C., Giacovazzo, C., Polidori, G. |
| Source: | Journal of Applied Crystallography. Dec2013, Vol. 46 Issue 6, p1592-1602. 11p. |
| Subjects: | Dual space, Electron density, Mathematical invariants, Crystal structure, Mathematical formulas, Crystallography |
| Abstract: | Third-generation direct methods programs are based on a phasing algorithm ( e.g. the tangent or the parameter shift method) and on dual space refinement techniques. The two spaces may be alternated during the phasing procedure or used in a sequential way: for example, first phase and after extend and refine. The tangent approach in SIR2011 belongs to the second category: phases are first estimated by the tangent formula, then their extension and refinement is performed in direct space via electron density modification techniques. In this article a number of new algorithms are described, with the aim of improving the SIR2011 tangent step and allowing more efficient phase extension and refinement. New criteria were chosen for defining the number of reflections to phase, for modifying the tangent weighting scheme, and for fixing the active use of the psi-0 triplets and of the quartet invariants. Each tangent trial may now be submitted to the RELAX procedure, a tool for moving to the correct position a well oriented but misplaced structural model. The resulting procedure shows surprising efficiency, testified by a wide set of applications. The experimental results have been compared with the tangent and VLD ( vive la différence) approaches implemented in SIR2011. [ABSTRACT FROM AUTHOR] |
| Copyright of Journal of Applied Crystallography is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
| Database: | Engineering Source |
| FullText | Text: Availability: 0 |
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| Header | DbId: egs DbLabel: Engineering Source An: 92016761 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
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| Items | – Name: Title Label: Title Group: Ti Data: A robust tangent procedure. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Burla%2C+M%2E+C%2E%22">Burla, M. C.</searchLink><br /><searchLink fieldCode="AR" term="%22Giacovazzo%2C+C%2E%22">Giacovazzo, C.</searchLink><br /><searchLink fieldCode="AR" term="%22Polidori%2C+G%2E%22">Polidori, G.</searchLink> – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Journal+of+Applied+Crystallography%22">Journal of Applied Crystallography</searchLink>. Dec2013, Vol. 46 Issue 6, p1592-1602. 11p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Dual+space%22">Dual space</searchLink><br /><searchLink fieldCode="DE" term="%22Electron+density%22">Electron density</searchLink><br /><searchLink fieldCode="DE" term="%22Mathematical+invariants%22">Mathematical invariants</searchLink><br /><searchLink fieldCode="DE" term="%22Crystal+structure%22">Crystal structure</searchLink><br /><searchLink fieldCode="DE" term="%22Mathematical+formulas%22">Mathematical formulas</searchLink><br /><searchLink fieldCode="DE" term="%22Crystallography%22">Crystallography</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: Third-generation direct methods programs are based on a phasing algorithm ( e.g. the tangent or the parameter shift method) and on dual space refinement techniques. The two spaces may be alternated during the phasing procedure or used in a sequential way: for example, first phase and after extend and refine. The tangent approach in SIR2011 belongs to the second category: phases are first estimated by the tangent formula, then their extension and refinement is performed in direct space via electron density modification techniques. In this article a number of new algorithms are described, with the aim of improving the SIR2011 tangent step and allowing more efficient phase extension and refinement. New criteria were chosen for defining the number of reflections to phase, for modifying the tangent weighting scheme, and for fixing the active use of the psi-0 triplets and of the quartet invariants. Each tangent trial may now be submitted to the RELAX procedure, a tool for moving to the correct position a well oriented but misplaced structural model. The resulting procedure shows surprising efficiency, testified by a wide set of applications. The experimental results have been compared with the tangent and VLD ( vive la différence) approaches implemented in SIR2011. [ABSTRACT FROM AUTHOR] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Journal of Applied Crystallography is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.) |
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| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1107/S0021889813024709 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 11 StartPage: 1592 Subjects: – SubjectFull: Dual space Type: general – SubjectFull: Electron density Type: general – SubjectFull: Mathematical invariants Type: general – SubjectFull: Crystal structure Type: general – SubjectFull: Mathematical formulas Type: general – SubjectFull: Crystallography Type: general Titles: – TitleFull: A robust tangent procedure. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Burla, M. C. – PersonEntity: Name: NameFull: Giacovazzo, C. – PersonEntity: Name: NameFull: Polidori, G. IsPartOfRelationships: – BibEntity: Dates: – D: 01 M: 12 Text: Dec2013 Type: published Y: 2013 Identifiers: – Type: issn-print Value: 00218898 Numbering: – Type: volume Value: 46 – Type: issue Value: 6 Titles: – TitleFull: Journal of Applied Crystallography Type: main |
| ResultId | 1 |
