High-throughput powder diffraction V: the use of Raman spectroscopy with and without X-ray powder diffraction data

In high-throughput crystallography it is possible to accumulate large numbers of powder diffraction patterns on a series of related compounds, often polymorphs, salts or co-crystals. In previous papers [Gilmore, Barr & Paisley (2004). J. Appl. Cryst. 37, 231–242; Barr, Dong & Gilmore (2004). J. Appl. Cryst. 37, 243–252] it has been shown how such data can be analysed by generating an (n × n) correlation matrix, ρ, by correlating n full powder diffraction patterns, point by point. The ρ matrix is used as a source of dendrograms and metric multidimensional plots in three or more dimensions which classify the patterns into sets related by similarity. In this paper, it is shown how Raman spectroscopy data can be used by themselves or as an adjunct to powder diffraction data by combining the two techniques using the individual differences scaling method (INDSCAL) of Carroll & Chang [Psychometria, (1970), 35, 283–319]. The method is very robust, and can be extended to other forms of spectroscopy. It is available as an option in the commercial PolySNAP3 computer program.