Monday, October 17, 2011

Limitations of PCM

A new paper claims to compute the pKa of nitrous acidium ion from gas phase DFT computations followed by estimation of solvation effects by a Polarizable Continuum Method (PCM). It is true that most often geometries do not change too much when going from gas phase to solution, but I strongly doubt the results are as accurate as they could be: PCM does not include the contribuiton from hydrogen bonds between the solute and the solvent, and I would expect that effect to be quite different in neutral HONO and protonated H2ONO+