ELF and Its Relatives-A Detailed Study About the Robustness of the Atomic Shell Structure in Real Space

A set of atomic shell indicators is presented based on the idea to express the positive kinetic energy density with a density-based ansatz multiplied by a modifying function. It is shown that all modifying functions reveal the atomic shell structure and all but one may serve as chemical bonding descriptors. This study reveals that the real space description of the atomic shell structure is very robust with respect to the proposed ansatz since all derived indicators exhibit the atomic shell structure very close to the ideal one or do not reveal a shell structure at all. (C) 2014 Wiley Periodicals, Inc.