Dear Brahma, Ga has a full d-shell. Therefore, if you try to perturb the d-shell of Ga, you can reduce the number of electrons localized on d-states by a positive Hubbard_alpha but there is no way to increase their occupations with a negative Hubbard_alpha. Therefore, the response matrices will be non-linear and you will get very small numbers in them. When you invert these matrices, very large numbers will appear.
Calculating U for full d-shells is not easy, and there is no simple solution (Another known example is ZnO). My personal opinion is that the use of LDA+U is questionable for filled d-shells. In fact if you check the paper mentioned by Matteo, the gap for GaAs is corrected by applying U and V (inter-site interactions) on Ga-p states and states which overlap with Ga-p. No correction on Ga-d is applied. Best regards, Burak On Sun, Oct 7, 2012 at 12:02 PM, Bramha Pandey <pandey.bramha at gmail.com>wrote: > sorry for wrong matrix copied in previous mail. > > CHI0^-1 - CHI^-1 Matrix > > 0.0000 0.0000 0.0000 > 0.0000 0.0000 0.0000 > > 0.0000 0.0000 0.0000 > type: 1 U0 = 0.000000000000000E+000 > > On Sun, Oct 7, 2012 at 10:30 PM, Bramha Pandey <pandey.bramha at > gmail.com>wrote: > >> Dear Prof. Matteo, >> i am using Ga, pseudo with 3d as a valence, Hubbard_l=2 is set for 'Ga'. >> If it should change how much value i have to set it? >> >> Dear sir i am totally struck by zero matrix element in ch0^-1 - chi^-1, >> so always it gifted me ZERO value where as ch0 and chi matrix are NON ZERO >> with same element value. >> CHI_0 Matrix >> -0.0002 -0.0002 0.0005 >> -0.0002 -0.0002 0.0005 >> 0.0005 0.0005 -0.0010 >> CHI Matrix >> -0.0002 -0.0002 0.0005 >> -0.0002 -0.0002 0.0005 >> 0.0005 0.0005 -0.0010 >> >> CHI0^-1 - CHI^-1 Matrix >> >> 0.0000 0.0000 >> 0.0000 0.0000 >> type: 1 U0 = 0.000000000000000E+000 >> This above is for all the 2 atoms supercell combination when we take the >> ZB structure with 2 atoms: (1) when both atoms are 'Ga' >> (2) when both atoms are 'Ga1' and 'Ga' (3) when both atoms are different >> 'Ga' and 'As'. >> >> All above three conditions are tested under one atom(Ga1 or Ga) is >> perturbed. >> Please Sir give me some ray of hope so that i can get rid of this >> situation. >> >> >> On Sun, Oct 7, 2012 at 8:10 PM, Matteo Cococcioni <matteo at umn.edu> wrote: >> >>> Dear Bramha, >>> >>> in J. Phys.: Condens. Matter 22 (2010) 055602 we did a similar >>> calculation but we got pretty different numbers (see Table 2 of the >>> reference). Maybe the states of Ga you applied U or alpha to are >>> completely full. what is the value of l set for Ga in set_hubbard_l ? >>> did you change that? also, for Ga, you better use a pseudo with 3d >>> states in the valence rather than frozen in the core. >>> >>> Matteo >>> >>> >>> >>> On Sun, Oct 7, 2012 at 7:31 AM, Bramha Pandey <pandey.bramha at gmail.com> >>> wrote: >>> > First of all thank you very much Dear Prof.Stefano. >>> > I have change the input as ZB 'GaAs' structure and calculate the 'U' >>> value >>> > for both 'Ga' and 'As' which is given bellow. >>> > But i wondered to see the 'U' value of 'Ga' 1010.79 which is quite >>> large so >>> > how can i figure out this is correct or wrong? >>> > No of Atom U_Ga U_As >>> > 2 1043.35792360332 2.87817590827985 >>> > 16 1010.81003743078 2.82970777976411 >>> > 54 1010.79529573193 2.82968584264055 >>> > 128 1010.79528904780 2.82968583269392 >>> > 250 1010.79528904476 2.82968583268940 >>> > Any comment is welcome. >>> > -- >>> > Thanks and Regards >>> > Bramha Prasad Pandey >>> > Ph.D Student Indian School of Mines(ISM) >>> > Dhanbad, INDIA. >>> > >>> > >>> > _______________________________________________ >>> > Pw_forum mailing list >>> > Pw_forum at pwscf.org >>> > http://pwscf.org/mailman/listinfo/pw_forum >>> >>> >>> >>> -- >>> Matteo Cococcioni >>> Department of Chemical Engineering and Materials Science, >>> University of Minnesota >>> 421 Washington Av. SE >>> Minneapolis, MN 55455 >>> Tel. +1 612 624 9056 Fax +1 612 626 7246 >>> _______________________________________________ >>> Pw_forum mailing list >>> Pw_forum at pwscf.org >>> http://pwscf.org/mailman/listinfo/pw_forum >>> >> >> >> >> -- >> Thanks and Regards >> Bramha Prasad Pandey >> Ph.D Student Indian School of Mines(ISM) >> Dhanbad, INDIA. >> >> > > > -- > Thanks and Regards > Bramha Prasad Pandey > Ph.D Student Indian School of Mines(ISM) > Dhanbad, INDIA. > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum > -------------- next part -------------- An HTML attachment was scrubbed... URL: http://pwscf.org/pipermail/pw_forum/attachments/20121007/4a39abd4/attachment-0001.html
