Accession Number:

ADA343620

Title:

Computationally Efficient Models for the Calculation of Structures and Properties of Materials

Descriptive Note:

Final rept. 15 Jan 94-14 Jul 97

Corporate Author:

ARKANSAS UNIV FAYETTEVILLE DEPT OF CHEMISTRY

Personal Author(s):

Report Date:

1998-03-18

Pagination or Media Count:

17.0

Abstract:

The goal of this research was to develop efficient methods for the determination of structures of complex molecular systems. Both the optimization strategy 1, and the generation of accurate potential energy functions 2 were addressed. Under 1, the PI concentrated on the role of coordinates adapted to molecular potential surfaces. His coordinates are widely used for medium-sized molecules where their rapid convergence greatly outweighs their extra cost. However, for large systems they become expensive. A naturalredundant coordinate optimization was developed with favorable computational cost and storage requirements. An efficient optimization method in inverse distance coordinates was implemented for Van der Waals clusters and for supramolecular optimization. Under 2, the PI further developed the localized correlation technique. He created a new program which allows correlated ab initio calculations on asymmetric molecules of unprecedented size. He also parametrized distant dispersion-like pair correlation energies their empirical inclusion greatly speeds up correlated calculations on large systems. Vibrational force fields were developed by scaling density functional force fields. These force fields accurately predict not only structures but also vibrational frequencies. A new definition of force constants in redundant coordinates was introduced, simplifying the parametrization and scaling of force fields.

Subject Categories:

  • Physical Chemistry
  • Computer Programming and Software

Distribution Statement:

APPROVED FOR PUBLIC RELEASE