Organa -: a program package for structure determination from powder diffraction data by direct-space methods

A new software package has been developed, named Organa, for ab initio solution of crystal structures from powder diffraction data by direct-space methods. The package contains energy-guiding Monte Carlo and grid-search algorithms and is based on a combined global minimization of the R factor and a potential energy function of the system with the option of local minimization of the cost function for each generated trial structure. Basically, the potential energy function consists of van der Waals interactions, but harmonic potentials can be added to impose soft distance restraints. The program was successfully applied to the structure determination of a series of melamine phosphate compounds. The program is freely available ( for all Windows platforms) from the correspondence author upon request.