ISOTOPE — Final force matrix written to disk (channel 9).
The keyword ISOTOPE causes the force constant matrix (also called the Hessian or second
derivative matrix) to be output to disk in a form
) 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.
FORCE and ISOTOPE are specified
in the same file, the force constants are read from disk. Isotope can only be used with
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