I fully agree with Emilio. The fact that you find negative PDOS even for s orbitals has to do with the interactions between those s-orbitals with the orbitals of the other atoms, which might give small negative contributions. If you select different orientations of the atoms, you may have different contributions from the atomic orbitals (since their orientation will not change) and those negative contributions could (hopefully) absorbed by other positive contributions. Thus, the PDOS will (hopefully) not be negative. Obviously, there is not any physical meaning for a negative PDOS. The problem comes from the physical meaning assigned to the PDOS, which is exactly the same with the physical meaning assigned to the Mullicken charges. Maybe you can get some answers in Roald Hoffmann's book "Solids and Surfaces".
Zacharias Fthenakis > The mentioned well-known problem is related with > the use of non-orthogonal basis sets. For > orthogonal ones the PDOS is definite positive, > which is what people expect. But for > non-orthogonal ones that is not the case > (although negatve values tend to be small > since the diagonal bit dominates and that one > is positive) > > Emilio > > -- > Emilio Artacho > CIC Nanogune Consolider, and Cavendish Laboratory, University of Cambridge > Tolosa Hiribidea 76, E-20018 Donostia - San Sebastián, Spain, > [email protected], +34 943 574 4000, http://theory.nanogune.eu > > On 12 Apr 2015, at 09:53, [email protected] wrote: > >> This is a well known "problem", but has not to do with SIESTA. It has to >> do with the physical meaning of the decomposition of DOS to PDOS. If you >> decompose to orbitals with different orientation you may probably not >> have >> those "problems". >> >> Zacharias Fthenakis >> >>> Dear siesta users, >>> Has any one encountered the problem of negative value of projected DOS >>> which is calculated with the mprop utility? It seems quite unreasonable >>> for me, any ideas how this come out? >>> >>> Best regards, >>> Bing >> >> >> ********************************************************* >> Dr Zacharias G. Fthenakis >> Research Associate >> Institute of Electronic Structure and Laser (I.E.S.L.) >> Foundation for Research and Technology Hellas (FO.R.T.H.) >> Vassilika Vouton P.O. Box 1527 71003 Heraklion Crete Greece >> Phone +30 2810 391824 >> FAX +30 2810 391305 >> webpage: http://esperia.iesl.forth.gr/~fthenak >> ********************************************************** >> > ********************************************************* Dr Zacharias G. Fthenakis Research Associate Institute of Electronic Structure and Laser (I.E.S.L.) Foundation for Research and Technology Hellas (FO.R.T.H.) Vassilika Vouton P.O. Box 1527 71003 Heraklion Crete Greece Phone +30 2810 391824 FAX +30 2810 391305 webpage: http://esperia.iesl.forth.gr/~fthenak **********************************************************
