The ISOTILT software for discovering cooperative rigid-unit rotations in networks of interconnected rigid units.

A user-friendly web-based software tool called ' ISOTILT ' is introduced for detecting cooperative rigid-unit modes (RUMs) in networks of interconnected rigid units ( e.g. molecules, clusters or polyhedral units). This tool implements a recently described algorithm in which symmetry-mode patterns of pivot-atom rotation and displacement vectors are used to construct a linear system of equations whose null space consists entirely of RUMs. The symmetry modes are first separated into independent symmetry-mode blocks and the set of equations for each block is solved separately by singular value decomposition. ISOTILT is the newest member of the ISOTROPY Software Suite . Here, it is shown how to prepare structural and symmetry-mode information for use in ISOTILT , how to use each of ISOTILT 's input fields and options, and how to use and interpret ISOTILT output.