And just to complete the story, some plane-wave codes do not do the muffin-tin analysis, but do a full projection onto atomic orbitals of the PW eigenstates, based on Sanchez-Portal et al; Solid St. Commun. 95, 685 (1995), and J. Phys. Condensed Matter 8, 3859 (1996). I think CASTEP and CPMD do this. In this case both the Mulliken charges and projected densities of states are conceptually the same as in Siesta. Mind you, the results will not be quantitatively comparable since in the case of PW they normally use a minimal (SZ) atomic basis set to project upon, while the original basis (PWs) is quite complete, while in Siesta the basis for the Mulliken analysis is the same as was used for the calculation.
Emilio On Jun 20, 2013, at 10:13 AM, [email protected] wrote: > Hi Benedikt, > Alberto is right, SIESTA does not need projections, > but YOU might need them; exactly for the sake of comparing > the charges with those from "muffin-tin"-type codes > I wrote some time ago a primitive tool > http://www.home.uni-osnabrueck.de/apostnik/Software/grdint.f > which "integrates" grid properties, e.g. charge (spin) densities, > over given (atom-centered) spheres. > Some remarks: > 1. It integrates functions defined on the grid, which are not > (l,m) resolved. That means, you can produce spin-up and spin-down > charges, but not partial s,p,d-charges. Of course you can first > generate LDOS within some energy interval, if you find it useful, > and then integrate it over a sphere. > 2. The "integration" is in fact merely a counting of grid points > which either fall within, or not, of a given sphere. So the result > is not very accurate and prone to "noise". But it is usually OK > for the sake of comparison, and anyway becomes "better" > as the mesh density is increased. > 3. The tool as not fast as you may expect it to be, for the task > it performs, because the algorithm used is very straightforward; > please feel free to improve. > > Best regards > > Andrei Postnikov > > > >> Hi Benedikt, >> >> SIESTA does not need projections, as the basis orbitals are localized on >> the atoms. You get naturally the "chemical" information one is used to. >> Plane-wave codes such as vasp do need projections to get some kind of >> "local" information from the delocalized basis. >> >> Alberto >> >> >> On Mon, Jun 17, 2013 at 4:28 PM, Benedikt Ziebarth < >> [email protected]> wrote: >> >>> Hello, >>> >>> I have a question about PDOS calculations with siesta. Is there a way to >>> specify the radius around the atoms in which the projection is carried >>> out? >>> This option exists in different other dft codes like vasp ( >>> http://cms.mpi.univie.ac.at/**vasp/vasp/RWIGS.html<http://cms.mpi.univie.ac.at/vasp/vasp/RWIGS.html> >>> ). >>> Any help would be very welcome. >>> Thanks >>> >>> Benedikt Ziebarth >>> >> > -- Emilio Artacho CIC nanoGUNE Consolider, and Cavendish Laboratory, University of Cambridge Tolosa Hiribidea 76, E-20018 Donostia - San Sebastián, Spain, [email protected], +34 943 574039, http://theory.nanogune.eu
