One-Electron Images in Real Space: Natural Adaptive Orbitals

We introduce a general procedure to construct a set of one-electron functions in chemical bonding theory, which remain physically sound both for correlated and noncorrelated electronic structure descriptions. These functions, which we call natural adaptive orbitals, decompose the n-center bonding indices used in real space theories of the chemical bond into one-electron contributions. For the n=1 case, they coincide with the domain natural orbitals used in domain-averaged Fermi hole analyses. We examine their interpretation in the two-center case, and show how they behave and evolve in simple cases. Orbital pictures obtained through this technique converge onto the chemist's molecular orbital toolbox if electron correlation may be ignored, and provide new insight if it may not. (c) 2015 Wiley Periodicals, Inc.