## Abstract

This chapter overviews the status of three dual-level approaches for potential surface calculations that use quantum mechanics for both the upper and lower level. Three types of approach are singled out for discussion: SEC and SAC calculations, IMOMO calculations with harmonically capped correlated small systems, and dual-level direct dynamics. The scaling external correlation (SEC) and scaling all correlation (SAC) methods are semi-ab initio approaches to the calculation of bond energies and barrier heights for chemical reactions. The IMOMO calculations are very similar in spirit to QM/MM methods, but the lower level is quantum mechanical. Dual-level direct dynamics is a general technique for combining levels in dynamics calculations that include quantum mechanical tunneling contributions.

Original language | English (US) |
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Pages (from-to) | 106-127 |

Number of pages | 22 |

Journal | ACS Symposium Series |

Volume | 712 |

State | Published - Dec 1 1998 |