Initially the code was developed under the VMS operating system, but the code is easily ported to UNIX machines. This version spreads the calculations for a large number of wave vector across the different processors, and is ideal for calculations of phonon density of states and diffuse scattering. We have found that RUMs act as soft modes for all the phase transitions we have investigated. A second aspect of this work has been to investigate the nature of high-temperature phases. For example, we found that in cristobalite there are enough RUMs to allow the tetrahedra to be orientationally disordered in the high-temperature phase.
Some zeolites have one or more RUMs for each wave vector.
These RUMs can be added together with appropriate phase factors to create local deformations in which the tetrahedra do not need to distort. One application of this approach has been to identify the mechanisms by which cations such as Ni can be held within zeolite structures. Moreover, we are quite happy to offer help to potential users. The programs can be obtained by downloading our compressed archive file rums. This archive file includes manuals and example input and output files, as well as the Fortran source codes.