IASTRT=integer and IAEND=integer. These allow one to request computation of just a
portion of a complete $vib info. "Vibs" will be
computed starting from the atom number IASTRT and
up to and including atom IAEND. Naturally, Hessian
will not be computed and vibrational analysis will
not be performed. The computed "$vib" information is
stored in the IRCDATA and PUNCH files. Use of these
options allows one to distribute large Hessian job
over very large number of nodes by splitting this job
into multiple independent parts.
Defaults are IASTRT=1 and IAEND=overall number of
atoms. These specific settings imply that a complete
$vib group will be computed, followed by the
computation of Hessian and vibrational analysis.
NOVIB0 (logical) When active, disables recomputation of wavefunction at
the initial geometry ("vib0") during numerical Hessian
restarts or when IASTRT/IAEND options are used.
Default is .false. i.e. wavefunction at the initial geometry
will be recomputed thus ensuring that computations of
all "vibs" will use the same initial guess for orbitals.
On Tue Dec 13 '16 11:49am, GrEv wrote
>I wonder if there is an option to calculate particular components of the Hessian matrix, from (a) particular atom(s). Such an option would be useful to parallelize frequency calculations, by 1) computing Hessian in parts on different machines, 2) merging together the $VIB sections from those calculations, and 3) restarting the calculation to diagonalize Hessian to obtain frequencies and normal modes. This would speed up frequency calculations very much.