Use existing MOs without new SCF cycle

How To
#1

I have an existing SCF result. I want to use that to compute a density cube for the molecule of interest. My $rem looks like this:

$rem
XC_GRID = 1
METHOD wB97M-V
SYMMETRY false
SYM_IGNORE true
BASIS def2-SVP
MEM_STATIC 10000
SCF_GUESS READ
MAX_SCF_CYCLES 0
MAKE_CUBE_FILES true
PLOTS true
$end

$plots
total_density 0
$end

However, the calculation spends 2 hours calculating new MOs. I don’t need new MOs. How do I get qchem to skip the duplicative MO calculation step and get it to go directly to just calculating the density cube from the existing MOs? The manual is no help.

Thanks for any help.

#2

What is happening is that it’s reading existing MOs as a guess, then starting the normal SCF procedure. Probably the DIIS error is very small if you’ve previously converged the SCF; however, the minimum number of SCF cycles is two (because that’s the minimum number that guarantees that F is consistent with P).

I believe that you can skip the SCF procedure altogether by setting SKIP_SCFMAN = TRUE in $rem.

#3

Thanks, John. I’ll use that for subsequent calculations.