Absolute hardness

Definition:

_LUMO - lowest unoccupied molecular orbital energy

_HOMO - highest occupied molecular orbital energy

References:

1. Z. Zhou, R. G. Parr, J. Am. Chem. Soc., 1990, 112, 5720.

2. R. G. Pearson, J. Org. Chem., 1989, 54, 1423.