Atom equivalents for converting DFT energies calculated on molecular mechanics structures to formation enthalpies

✍ Scribed by Rousseau, Emmanuelle; Mathieu, Didier

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 245 KB
• Volume: 21
• Category: Article
• ISSN: 0192-8651
• DOI: 10.1002/(sici)1096-987x(20000415)21:5<367::aid-jcc3>3.0.co;2-x

✦ Synopsis

New atom equivalents are introduced to convert BP/DN * * //MMFF energies into formation enthalpies. As a result of using molecular mechanics structures, poor results are obtained for compounds outside the scope of the force field, such as those bearing -NF 2 groups or some nitrogenous systems. Notwithstanding these limitations, present procedures compare well with the results of previous atom equivalents schemes. Indeed, rms deviations from experiment are below 9 kJ/mol for hydrocarbons, and close to 16 kJ/mol for a variety of compounds reasonably well described by MMFF. The explicit inclusion of thermal and vibrational contributions, using calculated frequencies, does not improve the results. This study demonstrates that cost-effective approaches to formation enthalpies may be developed on the basis of a combination of DFT with a suitable molecular mechanics force field.