[Wien] Cohesive energies warnings

[John Appleton]

  Dear Wien2k users,
   
  First, please forgive me if my questions are old and boring. 
  I am new to the electronic structure business so I get 
  bothered easily when things are not going right.
   
  I tried to compute the cohesive energy of silicon and Nitrogen, 
  following the description outline in the Wien2k FAQ. The 
  problem is that I get too many warnings . There is a warning attached to the 
  total energy and a warning that indicates that RKmax has 
  been reduced to NMATMAX. 
   
  I have read previous emails along this line but still don't get a 
  clear answer. I clearly understand that the Rkmax warning is due 
  the value to which NMATMAX in the source. But I have tried reducing the Rkmax 
  and RMT and I still get the warnings.  Even though the scf iterations converge, 
  the warning signs give me cause to to doubt (though previous emails tend to suggest 
  that it should not really matter) 
   
  My questions are:
   
  (1) For small atoms like Nitrogen and Silicon, what are the reasonable values of RMT 
  and Rkmax should be chosen without  getting warnings.
   
  (2) Say I perform the computation with a 30 Bohr FCC lattice and I get a 
  converged energy (hopefully without any warnings). How do I know for 
  sure that the result that I'm getting is reliable. Should I increase the lattice 
  constant, recomputed the energy and see the margin of error. If so, by how much do
   I increase the lattice constant, and for approximately how many lattice constants. In short, I want makes sure that I getting the right energies.  
   
  Thanks a million!
   
  John Appleton

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://zeus.theochem.tuwien.ac.at/pipermail/wien/attachments/20060110/762c92a8/attachment.html