Did you try (from one of Freeman's papers I believe): -Q*V_0(Q)/2 where Q is the excess charge of the cell (-ve for a negative cell) and V_0(Q) is the vacuum Coulomb potential in the calculation which is a function of Q which will depend upon the RMT.
Note the factor of 2. I don't think this is in Wien2k at the moment, it needs to be added retroactively (or could in principle be added to the code). It is a long time ago and I seem to remember that this worked for the empty cell test, but no longer have the data, so.... On Wed, Feb 24, 2010 at 3:18 PM, Peter Blaha <pblaha at theochem.tuwien.ac.at> wrote: > I've started some tests after the first query and it seems we might miss a > term in the total > energy. > > I created a clmsum-file (density) which is constant and is normalized to one > and put this into > a cell with a single H nucleus. > So it refers to the test case of a H+ ion in a lattice, where I do not add a > constant background, but > put the "background charge into case.clmsum. > > When one switches off the XC-terms, the resulting E-tot contains the > integral (rho *V-coul) and since > rho is constant (equal to Q/volume), we get the average potential in the > unit cell (not only the > interstital, where it is zero anyway) multiplied by the constant rho). > > This term is missing when I put a clmsum file with rho=zero, but add a > "background charge" > by case.inm, while the resulting potentials are identical for the two > methods. > > However, for a charged bulk system there is still a big problem, because > V-coul is determined > only up to a constant and is shifted arbitrarily such that the potential in > the interstital is zero. > In "neutral" calculations such a shift does not matter, since it will be > canceled by the sum of > eigenvalues, but when adding the constant background it matters. > > Thus, this correction term depends on RMT ? > > At the moment I'm not sure how I should continue. I think in other codes > such a correction is > added, but as mentioned, I guess the correction depends on the arbitrary > choice of V-zero. > > > Laurence Marks schrieb: >> >> Please see the next email on the >> list:http://zeus.theochem.tuwien.ac.at/pipermail/wien/2007-January/008713.html >> I think this is right and you take V0 from case.output0 (it is >> printedthere). You should do an empty cell test (no electrons) to verify >> thisand the units of V0, perhaps also looking at the code itself -- >> andremember to check the limit as the distance between atoms gets large. >> >> On Wed, Feb 24, 2010 at 11:05 AM, Yurko Natanzon<yurko.natanzon at gmail.com> >> wrote:> Dear Wien2k users and developers,> I'd like to refresh the >> discussion about the total energies of the> charged cells which took place >> three years ago:> >> http://zeus.theochem.tuwien.ac.at/pipermail/wien/2007-January/008711.html>> >> I'm trying to calculate the formation energy of the Hydrogen vacancy> in >> +/-1 charge states and find that the results are bad (much differ> from the >> literature) although the formation energy of the neutral> hydrogen vacancy >> is good. So my question arises if we can trust the> values of the total >> energies for the charged cells in the recent> version of Wien2k?>> To >> investigate this issue further I have performed the following> tests: I've >> done the calculations of the total energy of Mg, MgH2 and> GaN for three >> cases: neutral cell, cell with one electron removed (+1> charge) and a cell >> with an electron added (-1 charge). The results> were compared with the same >> calculati > > on with another plane-wave code> and are the following:> > -----------------------------------------> hcp Mg:> Wien2k:> E(+1)-E(0) = > 0.245 Ry> E(-1)-E(0) = -0.199 Ry>> Plane-Wave code:> E(+1)-E(0) = -0.226 Ry> > E(-1)-E(0) = 0.281 Ry>> bcc MgH2> Wien2k:> E(+1)-E(0) = 0.277 Ry> E(-1)-E(0) > = 0.085 Ry>> Plane-Wave code:> E(+1)-E(0) = 0.024 Ry> E(-1)-E(0) = 0.326 > Ry>> fcc GaN> Wien2k:> E(+1)-E(0) = 1.12 Ry> E(-1)-E(0) = -0.717 Ry>> > Plane-Wave code:> E(+1)-E(0) = -0.151 Ry> E(-1)-E(0) = 0.443 Ry> > ------------------------------------------------->> In wien2k the charged > cell was created by changing the number of> electrons in case.in2 and adding > the corresponding background charge> in case.inm. One can observe, that the > energies have the same order of> magnitude, but the sequence of energies > E(+1), E(0) and E(1) is> inverse. It seems, that the system with +1 charge > (electron removed)> behaves like the system with -1 charge in the Plane-Wave > code. Of> course, the results of tests are no > t physical, because no supercell> was used and no geometric relaxation was > performed (however, it is not> needed for Mg), but if one tries to do all > the supercell and> relaxation stuff and tries to calculate the defect > formation energy,> the result will be the same.>> I'd be grateful if you > comment on this and suggest any corrections> which should be provided to the > total energies for the charged cells.>> with kind regards,> Yurko>>> --> > Yurko (aka Yuriy, Iurii, Jurij etc) Natanzon> PhD student> Department for > Structural Research (NZ31)> Henryk Niewodnicza?ski Institute of Nuclear > Physics> Polish Academy of Sciences> ul. Radzikowskiego 152,> 31-342 Krakow, > Poland> E-mail: Yurii.Natanzon at ifj.edu.pl, yurko.natanzon at gmail.com> > _______________________________________________> Wien mailing list> > Wien at zeus.theochem.tuwien.ac.at> > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien> >> >> >> -- Laurence MarksDepartment of Materials Science and EngineeringMSE Rm >> 2036 Cook Hall2220 N Campus DriveNorthwestern UniversityEvanston, IL 60208, >> USATel: (847) 491-3996 Fax: (847) 491-7820email: L-marks at northwestern dot >> eduWeb: www.numis.northwestern.eduChair, Commission on Electron >> Crystallography of IUCRwww.numis.northwestern.edu/Electron crystallography >> is the branch of science that uses electronscattering and imaging to study >> the structure of matter._______________________________________________Wien >> mailing >> listWien at >> zeus.theochem.tuwien.ac.athttp://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > > -- > ----------------------------------------- > Peter Blaha > Inst. Materials Chemistry, TU Vienna > Getreidemarkt 9, A-1060 Vienna, Austria > Tel: +43-1-5880115671 > Fax: +43-1-5880115698 > email: pblaha at theochem.tuwien.ac.at > ----------------------------------------- > _______________________________________________ > Wien mailing list > Wien at zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > -- Laurence Marks Department of Materials Science and Engineering MSE Rm 2036 Cook Hall 2220 N Campus Drive Northwestern University Evanston, IL 60208, USA Tel: (847) 491-3996 Fax: (847) 491-7820 email: L-marks at northwestern dot edu Web: www.numis.northwestern.edu Chair, Commission on Electron Crystallography of IUCR www.numis.northwestern.edu/ Electron crystallography is the branch of science that uses electron scattering and imaging to study the structure of matter.
