SCF tolerance Dynamics DMol3

Dear all,
 
I have two questions:
1.- Which are the units for SCF tolerance in DMol3?
2.-  I set for SCF tolerance the value 1.0e-6 and 1000 max SCF cycles in Dynamics DMol3 but my work failed. I tried with all the parameters that speed up the convergence (DIIS size, smearing, preconditioner) and it failed again.  What can I do?
My system is porous silicon made using a 3x3x1 supercell.
 
Thanks in advance,
Best regards,
Marisol R. Arcos