EDMA: a computer program for topological analysis of discrete electron densities

EDMA is a computer program for topological analysis of discrete electron densities according to Bader's theory of atoms in molecules. It locates critical points of the electron density and calculates their principal curvatures. Furthermore, it partitions the electron density into atomic basins and integrates the volume and charge of these atomic basins. EDMA can also assign the type of the chemical element to atomic basins based on their integrated charges. The latter feature can be used for interpretation of ab initio electron densities obtained in the process of structure solution. A particular feature of EDMA is that it can handle superspace electron densities of aperiodic crystals in arbitrary dimensions. EDMA first generates real-space sections at a selected set of phases of the modulation wave, and subsequently analyzes each section as an ordinary three-dimensional electron density. Applications of EDMA to model electron densities have shown that the relative accuracy of the positions of the critical points, the electron densities at the critical points and the Laplacian is of the order of 10−4 or better.