Comparison of Koopmans' theorem
(HOMO
energy approximates ionzation energy)
Select species by entering formula
The following pages display the differences between the experimental ionzation energy
and the energy of the HOMO (highest occupied molecular orbital)
for a given molecule.
Koopmans' theorem states that the HOMO energy approximates the vertical ionization energy.
Rules for chemical formula
- Enter a sequence of element symbols followed by numbers
to specify the amounts of desired elements (e.g., C6H6).
- Elements may be in any order.
- If only one of a given atom is desired, you may omit
the number after the element symbol.
- Parentheses may be used to group atoms.
- Multiple specifications for an atom will be added.
This means that CH3(CH2)4CH3 will be
treated the same as C6H14.
- To specify one or more of a given atom, use a
question mark (?) after the element symbol.
- To specify any number (including zero) of given
element, use an asterisk (*) after the element symbol.
- A comma delimited list of several species may be entered.
Species in the CCCBDB
- Mostly atoms with atomic number less than than 18 (Argon). A few have Se or Br.
- Six or fewer heavy atoms and twenty or fewer total atoms.
Exception:
Versions 8 and higher have a few substituted benzenes with more than six heavy atoms.
Versions 12 and higher have bromine-containing molecules.
