DBGLOWDIN

Description

The Lowdin transformation (S^-1/2) is computed when keywords GRAPH, SYBYL, ESP, or MULLIKEN are present or when both NOVIS and VIS=MIN are absent. For full matrices, the overlap matrix is diagoalized and S^-1/2 is trivially computed from its eigenvalues and eigenvectores. Things are more complicated for the sparse matrix case because diagnalization cannot be used. S^-1/2 is formed from the overlap matrix S using a Chebyshev expansion strategy.

Using DBGLOWDIN causes diagnostic information about the Chebyshev expansion to be reported (for the sparse matrix case only). It also runs a test to determine the numerical accuracy of the resulting Lowdin transformation. This involves multiplcation and subtraction of matrices, so may take a non-trivial amount of time. This keyword does nothing if the Lowdin transform is not generated.