Direct methods for incommensurately modulated structures. On the applicability of normalized structure factors Version 4.0

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Direct methods for incommensurately modulated structures. On the applicability of normalized structure factors
DeGelder R, Israel R, Lam EJW, Beurskens PT, vanSmaalen S, Fu ZQ, Fan HF
ACTA CRYSTALLOGRAPHICA SECTION A 52: 947-954, Part 6 NOV 1 1996

Document type: Article

Language: English

Cited References: 21

Times Cited: 0

Abstract:
The recently defined normalized structure factors for incommensurately modulated structures [Lam, Beurskens & van Smaalen (1993). Acta Cryst. A49, 709-721] have been subjected to extensive tests regarding their applicability in direct methods for phase determination. It is shown that the probability distribution associated with the structure invariants E(-H)E(H')E(H - H'), where a and H' are reciprocal vectors of main and/or satellite reflections, approximately has the same functional form as the Cochran distribution but triplet phase relations are relatively less reliable when satellites are involved. The use of the multidimensional Sayre equation for the determination of phases of satellite reflections [Hao, Liu & Fan (1987). Acta Cryst. A43, 820-824; Fu & Fan (1994). J. Appl. Cryst. 27, 124-127] is not improved by using normalized structure factors instead of ordinary structure factors.

KeyWords Plus:
X-RAY-DIFFRACTION, ONE-DIMENSIONAL MODULATION, INTERGROWTH COMPOUNDS, CRYSTALS, SUPERSPACE, INTENSITY

Addresses:
DeGelder R, CATHOLIC UNIV NIJMEGEN, MAT RES INST, DEPT INORGAN CHEM, CRYSTALLOG LAB, TOERNOOIVELD 1, NL-6525 ED NIJMEGEN, NETHERLANDS.
CHRISTIAN ALBRECHTS UNIV KIEL, MINERAL PETROG INST & MUSEUM, D-24098 KIEL, GERMANY.
CHINESE ACAD SCI, INST PHYS, BEIJING 100080, PEOPLES R CHINA.

Publisher:
MUNKSGAARD INT PUBL LTD, COPENHAGEN

IDS Number:
VV956

ISSN:
0108-7673

Article 29 of 38