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An error assessment of single‐crystal 2πdata from four‐circle diffractometry
Author(s) -
Frevel L. K.,
Emge T. J.,
Kistenmacher T. J.
Publication year - 1983
Publication title -
journal of applied crystallography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.429
H-Index - 162
ISSN - 1600-5767
DOI - 10.1107/s0021889883010043
Subject(s) - diffractometer , crystal (programming language) , single crystal , crystallography , materials science , bar (unit) , matrix (chemical analysis) , crystal structure , physics , chemistry , computer science , meteorology , composite material , programming language
The criteria developed in the error analysis of 2 θ powder data for cubic and uniaxial phases [Frevel (1978). J. Appl. Cryst. 11 , 184–189] are extended to biaxial single‐crystal data. A methodology is described for applying the focusing matrix method to exhaustive sets of 2 θ data for pinacoid and prism reflections measured on a four‐circle diffractometer. A spheroidal crystal of hyperpure Si is used to calibrate a Syntex P automated diffractometer and to establish an effective wavelength for graphite‐monochromated Mo Kβ 1 β 3 radiation. A high‐quality single‐crystal of cis ‐[bis(7,9‐dimethylhypoxanthine) (ethylenediamine)platinum(II)] hexafluorophosphate, [Pt(C 2 H 8 N 2 )(C 7 H 8 N 4 O) 2 ].(PF 6 ) 2 , serves as a test case for comparing the normal least‐squared analysis with the focusing matrix method. It is concluded that an absolute accuracy greater than one part in 2000 for cell constants of biaxial crystals is difficult to achieve from automated four‐circle diffractometer data (2 θ ≤ 40°) for non‐spheroidal crystals with linear dimensions ca 0.2 mm.