The behavior here is what I might expect for a real-space DFT code, but V_NL is evaluated in reciprocal space right (we don't have real-space projectors)?
Just to double-check. Is charge density cutoff 4 times that planewave cutoff? On Wed, Oct 19, 2011 at 2:51 PM, William Parker <wparker at anl.gov> wrote: > Dear Yun Song and interested parties, > > The possibility of a phonon test case in ZnO piqued my curiosity so I decided > to have a go at it. ?I find a very odd convergence pattern with these two > pseudopotentials in this system--the total energy has a damped sinusoidal > decay with increasing cutoff: > (selecting the maxima and minima at 10 Ry sampling) > > E_cutoff (Ry) ? E_total (Ry) > 100 ? ? ? ? ? ? -338.741 > 160 ? ? ? ? ? ? -338.660 > 210 ? ? ? ? ? ? -338.675 > 290 ? ? ? ? ? ? -338.665 > 370 ? ? ? ? ? ? -338.668 > 400 ? ? ? ? ? ? -338.667 > > Figure here: > https://wiki.alcf.anl.gov/wparker/images/b/b5/ZnO_ecut_convergence_lda_ncpp.png > Details here: > https://wiki.alcf.anl.gov/wparker/index.php/Zinc_Oxide_Parameter_Convergence > > I have never encountered this kind of behavior with norm-conserving > pseudopotentials before. ?At worst, I've seen little steps in an otherwise > smooth convergence to a value. ?The eigenvalues at the various k-points don't > appear to have any ghost states that come and go with cutoff. ?Has anyone > observed this kind of oscillation in the total energy with increasing > plane-wave cutoff before? ?What gives rise to it? > > --William > > ********************************************************* > ?William D. Parker > ?Computational Postdoctoral Fellow ? fax: (630) 252-4798 > ?MSD-212, Rm. C-215 > ?Argonne National Laboratory > ?9700 S. Cass Ave. > ?Argonne, IL 60439 > ********************************************************* > > > > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > -- Nichols A. Romero, Ph.D. Argonne Leadership Computing Facility Argonne, IL 60490 (630) 447-9793
