CIF is an abbreviation for Crystallographic Information File, and these files record all of the information pertaining to crystal structure analysis. A CIF is written as a text file, and thus its content can be checked and edited using ordinary text editing software. CIFs are written with a special-purpose syntax, but they have spread rapidly due to their adoption by the IUCr (International Union of Crystallography), and are indispensible in X-ray structure analysis and related fields. In particular, when submitting papers whose focus is reporting the structure of a molecule, authors are frequently asked to submit a CIF, and there are likely many researchers who have struggled to understand and handle the alerts which appear during checking with checkCIF/PLATON on the IUCr website.
This paper discusses the purpose of and background behind the adoption of CIFs, alerts which frequently appear when checking using checkCIF/PLATON and how to handle them, details on judgment criteria, and vrf’s (validation reply/response forms). To deal with these alerts, one must first be familiar with checkCIF/PLATON, and the author will be thrilled if this paper serves as a opportunity for readers to improve their understanding.