Lee, T-S; Yang, W, *Frozen density matrix approach for electronic structure calculations*,
International Journal of Quantum Chemistry, vol. 69 no. 3
(1998),
pp. 397-404 .
**Abstract:**

*A frozen density matrix approach for determining local geometry changes of large molecules is proposed based on the density matrix divide-and-conquer method. This approach divides a large molecule into a small active part and the rest as the frozen part. After a single-point self-consistent field (SCF) calculation for the whole molecule, only the local molecular orbitals of the active part and its neighbor are updated when the geometry of the active part changes. The updated density matrix is calculated from the new local molecular orbitals of the active part and the stored local molecular orbitals of the frozen part. The electron transfer between the active and the frozen part is allowed via a common and variable chemical potential. The preliminary tests using semiempirical quantum chemical methods show this approach predicts the local geometry change well. The error in geometric parameters is less than 0.002 Å and less than 0.5° for bond length and bond angle, respectively. © 1998 John Wiley & Sons, Inc.*