Sodium parameters for AM1 and PM3 optimized using a modified genetic algorithm

Edward N. Brothers, Kenneth M. Merz

Research output: Contribution to journalArticle

26 Citations (Scopus)


Sodium is very important as a counterion in biology. However, when used with the most common semiempirical Hamiltonians, such as AM1 or PM3, sodium is modeled as a point charge that can accept no electron density, called a "sparkle". To better model sodium, we derived two sets of sodium parameters, which treat sodium on the same footing as other atoms parametrized in semiempirical methods. One set is compatible with the AM1 parameter set, while the second is compatible with PM3. These parameters were derived using a modified genetic algorithm with a diverse set of 71 compounds. The average unsigned error for the heats of formation was 10.3 kcal/mol for AM1 and 10.5 kcal/mol for PM3.

Original languageEnglish
Pages (from-to)2779-2785
Number of pages7
JournalJournal of Physical Chemistry B
Issue number10
Publication statusPublished - 14 Mar 2002


ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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