[DFTB-Plus-User] deprotonation energy of HNO3

[Debasis Sengupta]

I am trying to compute the deprotonation energy of nitric acid, HNO3  
(HNO3 --> H(+) + NO3-) to check the performance of DFTB against DFT 
calculation.  Here is what I get with DFTB1.1:
E(HNO3) = -12.6973122215 (hartree)
E(NO3-) =-12.3954402523  (hartree)
The deporotation energy at 0K is E(NO3-) + E(H(+)) - E(NO3-) = 
-12.3954402523 + 0 +12.6973122215 = 189.4 kcal/mol
I have used mio-1-1 and mio-0-1.  Both produce similar results.
This is quite different from the B3LYP -6-31+G(d,p) which is 318.5 
kcal/mol.  This value is with zero point correction. However, it should 
change much w/o zero point correction.
Any comment
Thanks
Debasis

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.zfn.uni-bremen.de/pipermail/dftb-plus-user/attachments/20111011/83b3d3e6/attachment.htm>