scispace - formally typeset
Journal ArticleDOI

Phase annealing in SHELX-90: direct methods for larger structures

George M. Sheldrick
- 01 Jun 1990 - 
- Vol. 46, Iss: 6, pp 467-473
Reads0
Chats0
TLDR
In this article, a phase annealing method, related to the simulated-annealing approach in other optimization problems, is proposed and it is shown that it can result in an improvement of up to an order of magnitude in the chances of solving large structures at atomic resolution.
Abstract
A number of extensions to the multisolution approach to the crystallographic phase problem are discussed in which the negative quartet relations play an important role. A phase annealing method, related to the simulated annealing approach in other optimization problems, is proposed and it is shown that it can result in an improvement of up to an order of magnitude in the chances of solving large structures at atomic resolution. The ideas presented here are incorporated in the program system SHELX-90; the philosophical and mathematical background to the direct-methods part (SHELXS) of this system is described.

read more

Citations
More filters
Journal ArticleDOI

Steric influence on the excited-state lifetimes of ruthenium complexes with bipyridyl-alkanylene-pyridyl ligands.

TL;DR: The large difference in measured excited-state lifetimes for the two homoleptic Ru (II) complexes is attributed to a strong influence of steric interactions on the ligand field strength, which in turn affects the activation barriers for thermal conversion from (3)MLCT states to short-lived ( 3)MC states.
Journal ArticleDOI

Geometric control of manganese redox state

TL;DR: In this article, a comparison of the structures of four monomanganese complexes of ligands with the identical donor [N3(O)-3] set reveals that geometry determines the redox state of the cation.
Journal ArticleDOI

Metal Complexes of Chiral Imidazolin-2-ylidene Ligands

TL;DR: In this paper, a general synthetic route to chiral 1,3-disubstituted imidazolin-2-ylidenes as well as the synthesis of several metal complexes of chirality of the starting materials during the synthesis is reported.
Journal ArticleDOI

Light- and thermal-induced spin crossover in [Fe(abpt)2(N(CN)2)2]. Synthesis, structure, magnetic properties, and high-spin low spin relaxation studies.

TL;DR: A quantitative light induced excited spin state trapping (LIESST) effect was observed, and the HS --> LS relaxation in the range of temperatures 5-52.5 K was studied.
Book ChapterDOI

[37] Patterson superposition and ab initio phasing

TL;DR: This chapter presents the possibility of the ab initio solution of macromolecular structures, given two unusually favorable circumstances: the availability of very high-resolution data and the presence of one or more heavier atoms, such as transition metals or even sulfur.
References
More filters
Book

Crystallographic Computing 3: Data Collection, Structure Determination, Proteins and Databases

TL;DR: The latest in a series on crystallographic computing, this collection of 33 papers covers the full spectrum of computer applications in crystallography, including the use of micro-, mini-, and mainframe computers.