Apologies. Beginning user and first time post. My name is Daniel and my affiliation is University of California Los Angeles (UCLA). Specifically, I am a Ph.D. candidate in the chemical engineering department at UCLA.
The simulations for the La2O3 slab with a surface O-atom removed are all identical (same 39 atom cell, same pseudopotentials, etc), except for differing in one or more of the following: degauss, etot_conv_thr, forc_conv_thr, mixing_ndim, upscale. The final energy results can vary widely, like between -8330 Ry to -8360 Ry, far too large of a distribution for the purposes the results are being used for. No such phenomenon happens when that O-atom is kept intact, energies consistent to within about 0.5 Ry. I get the "maximum number of steps reached" issue (possibly non-issue?) on all my simulations, O-atom intact or removed. I have a sample input file attached (converted from UNIX text to text format viewable in Windows). Output file was too big; not sure what samples to take from it that would help aside from previous general descriptions of what's going on. Thanks for any help you may have to offer. -- Daniel Noon UCLA Chemical and Biomolecular engineering On Fri, May 9, 2014 at 8:52 AM, Giuseppe Mattioli < giuseppe.mattioli at ism.cnr.it> wrote: > > Dear unknown user > First of all, please sign always your posts to this forum with your name > and scientific affiliation, we care about it :-) > > Regarding your questions, it is impossible to help you without seeing (at > least the relevant parts of) your input files. What do you mean when you say > "separate simulations" of the same system? Did you change the cell or the > vacuum region? Did you double the slab? Did you use different > pseudopotentials? > The second question can be also related to inconsistencies or errors in > your input files. Again, it is impossible to give you advice without seeing > them > > HTH > > Giuseppe > > On Friday 09 May 2014 07:57:20 noon at seas.ucla.edu wrote: > > Hello, > > > > I've been trying out pw.x, with my first goal being to reproduce some of: > > http://pubs.acs.org/doi/abs/10.1021/jp103604b. I've been running into > some > > issues and was wondering if I could get some advice: > > > > (1) When I run simulations of a La2O3 slab with a surface oxygen atom > > removed (39 atom supercell), I get wildly inconsistent results > (internally, > > on QE, when doing multiple simulations) for the energy when doing > "relax", > > with a range of about 30 Ry. The distribution of resulting energies from > > separate simulations seems to narrow when I tighten conv_thr, but I > cannot > > seem to get them to be acceptably consistent. Anyone familiar with this > > issue and how to address it? I appear to have no such problem when there > is > > no oxygen atom removed, with energies consistent within about 0.5 Ry. > > > > (2) For all of my simulations of La2O3 slabs, regardless of what my > inputs > > are and as long as I do not run into the maximum number of iterations for > > SCF or crash for another reason, I always eventually get the message "The > > maximum number of steps has been reached" with the simulation stopping. > > This message pops up even when it appears the number of SCF cycles and > BFGS > > steps do not reach nsteps. I notice that, during the simulations, it > seems > > to get to a point where the energy switches back and forth between two > > values between SCF cycles, and then eventually it decides to stop with > that > > message. Is there a fix for this? Or is this something I don't need to > even > > worry about (i.e. maybe the final result is acceptable)? > > > > Appreciate any advice you may have to offer. Can provide more information > > upon request. Thanks. > > > ******************************************************** > - Article premier - Les hommes naissent et demeurent > libres et ?gaux en droits. Les distinctions sociales > ne peuvent ?tre fond?es que sur l'utilit? commune > - Article 2 - Le but de toute association politique > est la conservation des droits naturels et > imprescriptibles de l'homme. Ces droits sont la libert?, > la propri?t?, la s?ret? et la r?sistance ? l'oppression. > ******************************************************** > > Giuseppe Mattioli > CNR - ISTITUTO DI STRUTTURA DELLA MATERIA > v. Salaria Km 29,300 - C.P. 10 > I 00015 - Monterotondo Stazione (RM) > Tel + 39 06 90672836 - Fax +39 06 90672316 > E-mail: <giuseppe.mattioli at ism.cnr.it> > ResearcherID: F-6308-2012 > > _______________________________________________ > 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/20140509/ed5bdad3/attachment.html -------------- next part -------------- A non-text attachment was scrubbed... Name: d.e.f.c.m.u.1D-4.1D-4.1D-3.1D-7.8.1D+3.in Type: application/octet-stream Size: 1934 bytes Desc: not available Url : http://pwscf.org/pipermail/pw_forum/attachments/20140509/ed5bdad3/attachment.obj
