EDF: Computing electron number probability distribution functions in real space from molecular wave functions Original Research Article

Given an N-electron molecule and an exhaustive partition of the real space (image) into m arbitrary regions image (image), the edf program computes all the probabilities image of having exactly image electrons in image, image electrons in image, and image electrons (image) in image. Each image may correspond to a single basin (atomic domain) or several such basins (functional group). In the later case, each atomic domain must belong to a single image. The program can manage both single- and multi-determinant wave functions which are read in from an aimpac-like wave function description (.wfn) file (T.A. Keith et al., The AIMPAC95 programs, , 1995). For multi-determinantal wave functions a generalization of the original .wfn file has been introduced. The new format is completely backwards compatible, adding to the previous structure a description of the configuration interaction (CI) coefficients and the determinants of correlated wave functions. Besides the .wfn file, edf only needs the overlap integrals over all the atomic domains between the molecular orbitals (MO). After the image probabilities are computed, edf obtains from them several magnitudes relevant to chemical bonding theory, such as average electronic populations and localization/delocalization indices. Regarding spin, edf may be used in two ways: with or without a splitting of the image probabilities into α and β spin components.