I have encounterd an issue when calculating the single Na ion at MP2/aug-cc-pVDZ level.
$molecule
1 1
Na 0.6984544449 -1.0075117274 0.3021673476
$end
$rem
SYM_IGNORE true
METHOD MP2
BASIS aug-cc-pVDZ
THRESH 14
SCF_CONVERGENCE 8
$end
The error message:
I also tried different basis set (e.g. cc-pVDZ), and attempted to adjust the “ao2mo_disk” keyword, but the error message still there.
Is anyone know what is the issue here?
Thanks.
This is an odd corner case that arises because the MP2 code defaults to frozen core, which makes Na+ a one-electron system for which it doesn’t make sense to do MP2 (because there isn’t a second electron to correlate). This causes Q-Chem to calculate the disk requirement for the calculation as zero, which you can see in your output, and the program crashes. You can resolve this, if you want, by setting N_FROZEN_CORE = 0 to correlate all electrons.
That said, I strongly suggest using RI-MP2 (with or without frozen core). Element Na doesn’t seem to be available in the aux basis for aug-cc-pVDZ (maybe because it’s unclear why Na needs diffuse functions), but is available for def2-SVP. The following input runs to completion:
$rem
SYM_IGNORE true
METHOD riMP2
aux_basis rimp2-def2-SVP
BASIS def2-svp
$end
Thank you for your help, John.