Other Search Types

The behaviour for other search types is as follows. SEARCH=1 specifies a pseudo-Newton-Raphson search where the formula for the steps is the same as the eigenvector-following step for search types 0 and 2, but we search uphill or downhill depending only upon the sign of the eigenvalue corresponding to the direction in question.[36] Of course, this step tends to the conventional Newton-Raphson step near a stationary point. For SEARCH=1 convergence to stationary points of any Hessian index is allowed.

Search types 3 and 4 are the same as 0 and 2 except that a pseudo-third derivative correction is applied to the step[36]. These search types are now redundant because dynamic scaling using a trust radius and separate maximum step sizes for each direction seems to work much better (see §VI).

Search type 5 is the same as type 0 except that the system is rotated into principal axes in the setup step.

Search types 6 and 7 are for steepest-descent energy minimizations using the Page-McIver method[37] with analytic first and second derivatives at each step. Search type 7 can converge to a saddle point, search type 6 can only converge to a true minimum.

Search type 8 is a steepest-ascent transition state search using a modification of the Page-McIver steepest-descent algorithm.