Koopmans' Theorem Comparison of Ionization Energy for a set of speciesSelect a species by entering a chemical formula. or choose by chemical groups.
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.
- Ions are indicated by placing + or - at the end of the formula (CH3+, BF4-, CO3--)
Species in the CCCBDB
- Mostly atoms with atomic number less than than 36 (Krypton), except for most of the transition metals. See section I.B.1 for a periodic table view.
- 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.
Going to the group selection page allows the selection of molecules with certain chemical groups, such as C=O bonds or NH2 groups. A list of species that match the group criteria is returned and one or more may be selected.
Caution! Choosing a long list may take a long time to to load. For example: 150 species takes about a minute.