A short history of SHELX

Abstract

An account is given of the development of the SHELXsystem of computer programs from SHELX-76 to the present day. In addition to identifying useful innovations that have come into general use through their implementation in SHELX, a critical analysis is presented of the less-successful features, missed opportunities and desirable improvements for future releases of the software. An attempt is made to understand how a program originally designed for photographic intensity data, punched cards and computers over 10000 times slower than an average modern personal computer has managed to survive for so long. SHELXLis the most widely used program for small-molecule refinement and SHELXSand SHELXDare often employed for structure solution despite the availability of objectively superior programs. SHELXLalso finds a niche for the refinement of macromolecules against high-resolution or twinned data; SHELXPROacts as an interface for macromolecular applications. SHELXC, SHELXDand SHELXEare proving useful for the experimental phasing of macromolecules, especially because they are fast and robust and so are often employed in pipelines for high-throughputphasing. This paper could serve as a general literature citation when one or more of the open-source SHELXprograms (and the Bruker AXS version SHELXTL) are employed in the course of a crystal-structure determination.