ISOTOPE 

Description

The keyword ISOTOPE causes the force constant matrix (also called the Hessian or second derivative matrix) to be output to disk in a form (jobname.res) readable for subsequent calculations, whether or not the calculation has been completed. This is especially useful for kinetic isotope effect (KIE) studies where the force constants do not change, only the reduced masses of the atoms. Full diagonalization of this matrix of second derivatives of energy with respect to nuclear position is very CPU intensive and ISOTOPE may be used with RESTART for lengthy frequency calculations. If RESTART, FORCE and ISOTOPE are specified in the same file, the force constants are read from disk. Isotope can only be used with FORCE, LTRD, and NEWTON.

See also:

OLDENS, DENMAT, RESTART