A test of the new “integrated MO + MM” (IMOMM) method for the conformational energy of ethane and n-butane
✍ Scribed by Toshiaki Matsubara; Stefan Sieber; Keiji Morokuma
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 697 KB
- Volume
- 60
- Category
- Article
- ISSN
- 0020-7608
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✦ Synopsis
Test calculations of the newly developed "Integrated Molecular Orbital + Molecular Mechanics" (IMOMM) method were performed for the optimized equilibrium and transition structures and energies of ethane and n-butane. In this method, the total energy of a large molecular system is expressed as a sum of the MO energy of the small "model" system and a modified MM energy of the "real" system, and full geometry optimization is carried out using the gradient of this total energy. Various schemes of partition of the system into the MO part and the MM part, including some not intended in the original design of the method, were examined and compared with the pure ab initio MO and the pure MM results. In most reasonable partition schemes, the IMOMM method can reproduce the pure ab initio and the pure MM geometries and energies quite well. 0 1996 John Wiley & Sons, Inc. tion, and biological systems [ll. However, it is not accurate enough to treat strong molecular interactions where large charge transfer or electron reorganization is involved. For instance, no general he mckcular mechanics (MM) methods with molecular mechanics method has been developed
T molecular force fields such as MM2, MM3, which can predict transition-state structures and C h a r m , Amber, and UFF have been used energies of chemical reactions, though some effort for large and as-has been made to extend the force to cover some semblies including large organic molecules, soh-limited transition states [21. For strong chemical interactions such as chemical reactions, high-level