Buy article online - an online subscription or single-article purchase is required to access this article.
Download citation
Download citation
link to html
A method is described to search for the most probable assignment of indices to powder diffractograms starting from approximate unit-cell parameters. The difference ΔQi = ΔQoi−ΔQci between observed and calculated quadratic forms of the ith peak is attributed to three contributions: ΔQi* due to imprecise unit-cell constants, ΔQi′ due to incorrect indexing and [epsilon]i due to experimental error. The points ΔQi plotted as a function of ΔQoi give rise to distributions D′, D* (or under special conditions Dg*) and D[epsilon]. The differences between these distributions are evinced by differences in their moments and probability function. At the start the nearly normal distribution Dg* is searched for, by changing the initial reciprocal-cell parameters by small increments δa*, δb*, δc*. Highly probable indices can then be assigned to the Qoi's and the unit-cell constants refined by the least-squares method. At the end the normal distribution D[epsilon] with mean μ = 0 must be obtained. Statistically significant deviations of D[epsilon] from the normal distribution with μ = 0 indicate that some systematic experimental errors affect the data. The method is suitable for applications to electronic computers and is particularly recommended for plotters.

Subscribe to Journal of Applied Crystallography

The full text of this article is available to subscribers to the journal.

If you have already registered and are using a computer listed in your registration details, please email support@iucr.org for assistance.

Buy online

You may purchase this article in PDF and/or HTML formats. For purchasers in the European Community who do not have a VAT number, VAT will be added at the local rate. Payments to the IUCr are handled by WorldPay, who will accept payment by credit card in several currencies. To purchase the article, please complete the form below (fields marked * are required), and then click on `Continue'.
E-mail address* 
Repeat e-mail address* 
(for error checking) 

Format*   PDF (US $40)
In order for VAT to be shown for your country javascript needs to be enabled.

VAT number 
(non-UK EC countries only) 
Country* 
 

Terms and conditions of use
Contact us

Follow J. Appl. Cryst.
Sign up for e-alerts
Follow J. Appl. Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds