Convergence of mBJ calculations is sometimes a bit tricky since not only the charge density but also the kinitic energy density (or the "vresp"-files) determine the potential.
The recommended way is to start out with a PRATT mixing (with eg. 0.2) and once the :DIS has settled a bit (decreased from the initially big values, but then not changing much, usually after ~10 iterations) one can graduadely increase the mixing factor (to eg. 0.3 and 0.4). Maybe :DIS increases a little, but as long as there are no oszillations in :ENE or :GAP this is fine. Eventually, one may intermediately "save" the calculations (to have a restarting point) and continue with MSEC1, since once the vresp-files are partially converged, density-mixing as done with MSEC1 should be fine. Please be aware, that in mBJ-calculations not only the density (clmsum) is mixed, but that the mixing-factor in case.inm also mixes the exchange-potential in lapw0. Thus, there is a danger of "pseudo-convergence" when the mixing factor is too small. Am 09.01.2011 00:31, schrieb David: > Dear Professor Blaha and Wien users, > > I'm running mBJ calculations for CuZrTiO5, spin-polarized, it has 16 > atoms in the unit cell, and im running 300 k-points. My ultimate goal is > to get the band structure of this crystal. > > I haven't got any problems regarding code errors, in fact up to now > everything has run very smooth. My question though is the following: the > has has run 58 cycles now and the charge distance does not seem to > reduce significantly, in fact for the first 45 cycles or so it reduced > very slow, but now it's going up again, I was wondering if this is a > common behaviour? Also I was wondering if there is any way I can make it > converge faster, I know this is a large calculation, but may be some of > you guys have suggestions. > > Some details about my calculation: > > 1. I run a regular spin-polarized scf cycle using the MSEC1 with a > mixing factor of 0.2 and it converged in 18 cycles (convergence criteria > was charge: 0.00001 e) > > 2. I followed the steps for mBJ calculations from the manual, I used > PRATT with a mixing factor of 0.2 and the convergence criteria is > charge: 0.00001 e > > 3. Attached are the case.struct and case.inst if it helps > > Please if you required any other information in order for me to get some > help, I can send it > > Thank you very much > > David Guzman > Department of Physics > California State University - Los Angeles > > > > _______________________________________________ > Wien mailing list > Wien at zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien -- Peter Blaha Inst.Materials Chemistry TU Vienna Getreidemarkt 9 A-1060 Vienna Austria +43-1-5880115671
