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Phasing via pure crystallographic least squares: an unexpected feature
Author(s) -
Burla Maria Cristina,
Carrozzini Benedetta,
Cascarano Giovanni Luca,
Giacovazzo Carmelo,
Polidori Giampiero
Publication year - 2018
Publication title -
acta crystallographica section a
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.742
H-Index - 83
ISSN - 2053-2733
DOI - 10.1107/s2053273318001407
Subject(s) - phaser , least squares function approximation , convergence (economics) , feature (linguistics) , crystallography , crystal structure prediction , obstacle , algorithm , crystal structure , materials science , computer science , mathematics , chemistry , physics , statistics , optics , linguistics , philosophy , estimator , political science , law , economics , economic growth
Crystallographic least‐squares techniques, the main tool for crystal structure refinement of small and medium‐size molecules, are for the first time used for ab initio phasing. It is shown that the chief obstacle to such use, the least‐squares severe convergence limits, may be overcome by a multi‐solution procedure able to progressively recognize and discard model atoms in false positions and to include in the current model new atoms sufficiently close to correct positions. The applications show that the least‐squares procedure is able to solve many small structures without the use of important ancillary tools: e.g. no electron‐density map is calculated as a support for the least‐squares procedure.