[Pw_forum] cohesive energy of water/ice

[Martin Andersson]

Hi again,

There is at most 0.01 eV cohesive energy difference when changing the 
box size or using nosym and assume_isolated='mp' or 'mt'. This has also 
been my experinece from other neutral molecules that a large box by 
itself provides reliable gas phase reference energies.

Any other suggestions? I have tried both ultrasoft pseudopotentials and 
PAW, both of which have been checked for plane wave convergence, so I am 
really at a loss. Could the literature calculations with VASP really be 
so wrong? I feel it is more likely that I have made some mistake...

Cheers,
Martin Andersson
University of Copenhagen