Dear Rajdeep Banerjee, In a recent paper of mine (http://dx.doi.org/10.1021/jp306160c) I used the van de Walle & Martin's scheme, later used by Pasquarello, to compute the band alignment at ZnO/TiO2(anatase) interfaces. The purely electrostatic (ionic + Hartree) potential was used as reference. At least the results agreed with experimental observations from Gr?tzel's group on certain DSSCs. What I would stress here is that one should pay attention also (as I did in that work) to the need of obtaining as reliable VB and CB positions as possible - which implies at least a good reproduction of the bandgap, a well known issue. A way to do so, without having to carry out rather expensive GW calculations, may be to use a PBE0 hybrid functional with the fraction of HF exchange tuned to the optical dielectric constant (a suggestion by Lucia Reining's group); see the mentioned paper as well as http://dx.doi.org/10.1016/j.cattod.2012.08.039 for details and references. Good luck, Jos? Carlos
El 04/06/2014 14:10, Sclauzero Gabriele escribi?: > Dear Rajdeep Banerjee, > > I think what is used as reference potential is the bare ionic potential > + Hartree potential (V_bare + V_H). I kind of justification for that is given > in this older paper by van de Walle & Martin > (http://journals.aps.org/prb/pdf/10.1103/PhysRevB.35.8154) about band lineups > at heterointerfaces. > > I agree with Nicola that the problem is subtle, given that a pure bulk > calculation for an infinite solid cannot provide absolute energy levels. > Hopefully someone with clearer ideas than me will be able to suggest > alternative solutions. > > Best, > > GS > > > Dear Sclauzero Gabriele, > I looked at the paper you suggested > (http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.101.046405) where it was > said that the "common reference level (phi) " is calculated as the "cell > average of the local potential originating from the ionic pseudopotentials" > which I guess can be calculated from the pseudopotentials used. Can you > suggest any functional form for this calculation of phi ? or indicate how to > generate it from the pseudopotentials used? > > As far as I understand, after defining phi, the CBM and VBM can be described > by: > > > CBM = Ec - phi > VBM = Ev - phi > > where Ec and Ev are LUMO and HOMO respectively. > > Thank you very much for all the help. > > Rajdeep Banerjee > JNCASR, > Bangalore, India > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org<mailto:Pw_forum at pwscf.org> > http://pwscf.org/mailman/listinfo/pw_forum > > > Dr. Gabriele Sclauzero > Materials Theory - ETHZ > ETH Zurich, HIT G 43.2 > Wolfgang-Pauli-Str. 27 > 8093 Z?rich, Switzerland > > Phone +41 44 633 94 10 > Fax +41 44 633 14 59 > gabriele.sclauzero at mat.ethz.ch<mailto:gabriele.sclauzero at mat.ethz.ch> > www.theory.mat.ethz.ch > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum -- Jos? C. Conesa Director Instituto de Cat?lisis y Petroleoqu?mica, CSIC Marie Curie 2, Cantoblanco 28049 Madrid - Spain Tel. +34-915854766
