Match! identifies phases in a sample by comparing its powder diffraction pattern to reference patterns of known phases. Hence, it needs a so-called "reference database" in which these reference patterns are provided. The reference databases are managed in the so-called "Reference Database Library" dialog.
There are several options for obtaining a reference database:
In this context, we would like to thank Pete Strickland (IUCr), Armel Le Bail (COD) and Bob Downs (AMCSD) for their kind permission to download and distribute their data free-of-charge!
All entries of the "COD" reference database contain atomic coordinates, based on which the corresponding powder diffraction patterns have been calculated. Besides this, for all entries, I/Ic-values have been calculated, so that a semi-quantitative analysis can be carried out.
You can download additional or updated reference databases free-of-charge from
Many users also have diffraction patterns of own compounds which are not (yet) present in the COD or PDF databases. Hence, it is desirable to use these patterns in phase identification in addition to the "normal" patterns. This can be achieved using the so-called "user database".
We have run several tests in order to evaluate the quality of the various reference databases mentioned above:
Compared to using the classical ICDD PDF database, our tests reveal a somewhat diverse performace when using the free-of-charge COD reference patterns: When mineral samples were investigated, the results were generally very good, thanks to the excellent coverage of the AMCSD (which is included in the COD). Even for many samples other than minerals, the correct phases were identified in most cases, however, we found some (few) samples where main phases were not recognized because the corresponding reference patterns were not present in the COD reference database. In all cases, it was no problem to identify all phases when using the ICDD PDF-2 Release 2007 database.
According to our experience, it is optimal to combine the COD database (which basically contains more recent entries) with a user database created from ICSD/Retrieve (which typically contains "older" entries). Using such a combined reference database is the best solution if you do not have a recent ICDD PDF database available!
Hence, if you are investigating mineral or similar samples, you should be fine using the free-of-charge COD reference database. For most other users, it is currently advisable to either add ICSD/Retrieve reference patterns to the COD database, or use the conventional ICDD PDF-2 or PDF-4 database.