Dear Paolo, that's why, I only quoted and argued on energy differences.
However, they seem to be too far away from expectation (10-fold). Is there any normalisation to be made? Dividing by the number of molecules per unit cell (if there is one per asymmetric unit, this would refer to 8 for an orthorombic case, e.g.)? I'm not sure, what the "reference" of the calculated Rydberg value is - if it would be the whole cell, I would get doubled energy values and differences when I calculate a 2x1x1 supercell... The other way round: what does "per mole" really mean in a conversion of "some amount" to "a mole" (e.g.: Joule to Joule/mol)... Thanks for helping me! Am 21.03.2012 19:14, schrieb Paolo Giannozzi: > > On Mar 21, 2012, at 17:05 , Alex Kutana wrote: > >> There is a search function for the pw_forum, although It's well hidden > > there are two search functions, both linked and well visible in the > "Contacts" page of the QE web site. > > About the original qeustion: QE calculates total energies per unit cell, > in Ry. The absolute value of the energy depends upon the specific > set of pseudoppotential and has no physical meaning; energy differences > have physical meaning > > P. > --- > Paolo Giannozzi, Dept of Chemistry&Physics&Environment, > Univ. Udine, via delle Scienze 208, 33100 Udine, Italy > Phone +39-0432-558216, fax +39-0432-558222 > > > >
