Hi, QE uses Ry. I believe that CASTEP uses Ha. There is your factor 2.
Cheers, Martin Andersson University of Copenhagen On 8 nov 2013, at 12:37, Michael Fischer <dommiguel at gmx.de> wrote: > Hello everyone, > > I am trying to do some single point calculations for a porous system > including a guest molecule using QuantumEspresso 5.0.2, employing the > PBE functional and the Grimme-type dispersion correction (London=.true., > other related parameters on default settings). > > When comparing my results to earlier calculations using CASTEP with > comparable settings, I found rather large differences, and it became > clear quite quickly that the majority of these differences are due to > the dispersion interactions. Below, I have extracted the dispersion > contribution to the total energy (in Ry) obtained with the two different > codes (sorry for awkward formatting): > > CASTEP QuantumEspresso > Zeo -0.11569 -0.23136 > Guest -0.00010 -0.00020 > Zeo + Guest -0.12646 -0.25290 > > It turns out that the dispersion energy from QuantumEspresso is > practically exactly twice as large as the energy calculated by CASTEP. > Looking at previous literature studies, I have good reason to "trust" > the CASTEP energies (they are at least in the right ball park), while I > must assume that the QE results are too large. Is this problem known to > anyone? > > I should possibly add that I successfully ran the test that involves the > Grimme-type correction (the dispersion contributions in vdw.out and > vdw.ref are the same). > > Any help will be greatly appreciated. > Kind regards, > Michael > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum
