I am trying to run single point calculations with Gaussian 09 for a Mulliken population analysis on large graphene/graphite (940-1411 atoms) sheets/clusters.
I was having difficulty with memory issues (single CPU license) running DFTBA
for single point calculations. I have stepped my convergence (beginning with conver=1
, and increasing by reading in my previous checkpoint files). I found my results oscillating and failing.
I decided to try scf=(qc,conver=5,maxcycle=500)
. This worked, which concerned me.
It not only worked, but it worked much faster than my failed sp
calculations. I know Gaussian's old default convergence for single point calculations was N=4. As my calculation was done in less than two hours compared to the days it was taking for DIIS
, I have become concerned at the accuracy of the QC using conver=5
. I cannot find anything indicating my approach is bad, but also I cannot find anything syaing my approach should yield reasonable results.
Can anyone please tell me if this approach is reasonably accurate?