Does the Intra-atomic Deformation Energy of IQA Represent Steric Energy?

We show that the mutual, through-space compression of atomic volume experienced by approaching topological atoms causes an exponential increase in the intra-atomic energy of those atoms regardless of approach-orientation. This insight was obtained using the modern energy partitioning method called Interacting Quantum Atoms (IQA). This behaviour is consistent for all atoms except hydrogen, which can behave differently depending on its environment. Whilst all atoms experience charge transfer when they interact, the intra-atomic energy of the hydrogen atom is more vulnerable to these changes than larger atoms. The difference in behaviour is found to be due to hydrogen’s lack of a core of electrons which, in heavier atoms, consistently provides repulsion when compressed. As such, hydrogen atoms do not always provide steric hindrance. In accounting for hydrogen’s unusual behaviour and demonstrating the exponential character of the intra-atomic energy in all other atoms, we provide evidence for IQA’s intra-atomic energy as a quantitative description of steric energy.