Re: CCL:Correction of Koopmans ionization potentials

[Russell D Johnson III <russell.johnson ~~ nist.gov>]

Hello,
   The NIST CCCBDB (Computational Chemistry Comparison and Benchmark Database)
 has some experiment vs theory comparisons of Koopman's ionization potentials. It
 provides differences rather than ratios, but a cursory glance makes it look like
 a general multiplication factor will not do very well.
 The CCCBDB is online at:
 http://srdata.nist.gov/cccbdb
 See section IV.E.3 and try entering C?H? to get a list of hydrocarbons.  After
 selecting some or all the molecules from the list choose the table cell for
 HF/6-31G*. The differences range from -0.5 to 1.7, which doesn't look easy to
 correct using a scale factor. Even if you choose a subset, such as molecules
 with a carbon-carbon triple bond, there is still a spread.
 At 09:58 AM 2005-05-09, you wrote:
 >Dear colleagues,
 >
 >I heard that the Koopmans ionization potentials (HF method) can be
 >corrected by a multiplication factor of about 0.92, but I am not sure it
 >is true.
 >Could anybody provide me some references to the corrections of Koopmans
 >ionization potentials?
 Dr. Russell D. Johnson III
 Research Chemist
 National Institute of Standards and Technology
 Computational Chemistry Group
 100 Bureau Drive, Stop 8380
 Gaithersburg, MD 20899-8380
 voice: 301+975-2513 fax:301+869-4020
 email: russell.johnson ~~ nist.gov