<div dir="ltr"><div>Hello again,</div><div><br></div><div>have tried some attempts to start calculation with WAVELET poisson solver, but all attempts have failed due to following error messages:</div><div><br></div><div>1) the FFT in the x direction is not allowed<br> n01 dimension 154</div><div> (pw/ps_wavelet_util.F:358)</div><div><br></div><div> ===== Routine Calling Stack ===== <br><br> 13 S_FFT_dimensions<br> 12 RS_z_slice_distribution<br> 11 ps_wavelet_create<br> the FFT in the x direction is not allowed<br> n01 dimension 154<br> 10 pw_poisson_rebuild<br> 9 pw_poisson_solve<br> 8 qs_ks_build_kohn_sham_matrix<br> 7 rebuild_ks_matrix<br> the FFT in the x direction is not allowed<br> n01 dimension 154<br> the FFT in the x direction is not allowed<br> n01 dimension 154<br> the FFT in the x direction is not allowed<br> n01 dimension 154<br> the FFT in the x direction is not allowed<br> n01 dimension 154<br> 6 qs_ks_update_qs_env<br> 5 scf_env_do_scf_inner_loop<br> 4 scf_env_do_scf<br> 3 qs_energies<br> 2 qs_forces<br> 1 CP2K<br></div><div><br></div><div><br></div><div>2) after that I turn off the command EXTENDED_FFT_LENGTHS, then:</div><div><br></div><div> Index to radix array not found.</div><div> (pw/fft_tools.F:293)</div><div><br></div><div> ===== Routine Calling Stack ===== <br><br> 6 pw_grid_setup<br> 5 pw_env_rebuild<br> 4 qs_env_rebuild_pw_env<br> 3 qs_env_setup<br> 2 qs_init_subsys<br> 1 CP2K<br></div><div><br></div><div></div><div><br></div><div>That's strange and I don't know what to do. <br></div><div>In my input file there are some info about commands:</div><div><br></div><div>[...]<br></div><div> SURFACE_DIPOLE_CORRECTION .TRUE.<br> SURF_DIP_DIR Y<br></div><div>[...]<br></div><div> &MGRID<br> CUTOFF 600<br> NGRIDS 5<br> REL_CUTOFF 50<br> &END MGRID<br></div><div>[...]</div><div> &POISSON<br> POISSON_SOLVER WAVELET<br> PERIODIC XZ<br> &END POISSON<br></div><div>[...]</div><div><br></div><div>[...]<br></div><div> &CELL<br> A 5.148 0.0 0.0<br> B 0.000 100.0 0.0<br> C 0.0 0.0 8.9166 <br> PERIODIC XZ<br> &END CELL<br></div><div>[...]</div><div><br></div><div>Phil</div><div><br></div><div><br></div>Am Donnerstag, 10. Januar 2019 10:56:24 UTC+1 schrieb Phil G.:<blockquote class="gmail_quote" style="margin: 0;margin-left: 0.8ex;border-left: 1px #ccc solid;padding-left: 1ex;"><div dir="ltr"><div>Dear Matt,</div><div><br></div><div>how can find the potential in the vacuum (which type of potential? potential energy or electric/electrostatic potential?) ?</div><div>For the case of electric/electrostatic potential, there is a flat curve with a step near the vacuum center as a consequence of dipole correction in Z direction, while in the bulk slab there is a periodic curve. <br></div><div><br></div><div>I will try to use the wavelet solver with PERIODIC XY.</div><div><br></div><div>Phil<br></div><br>Am Mittwoch, 9. Januar 2019 14:05:04 UTC+1 schrieb Matt W:<blockquote class="gmail_quote" style="margin:0;margin-left:0.8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Hello again,<div><br></div><div>did you find the potential in the vacuum and align to that? You need to set a reference to get absolute values.</div><div><br></div><div>You could also try using the wavelet solver </div><div><br></div><div>&POISSON</div><div> PSOLVER WAVELET</div><div> PERIODIC XZ<br>&END</div><div><br></div><div>and PERIODIC XZ in the &CELL section. The Y direction must be the non-periodic one. That gives an absolute reference (if there is no dipole in the cell otherwise you need the dipole correction switched on).</div><div><br></div><div>Matt</div><div><br>On Wednesday, January 9, 2019 at 8:18:58 AM UTC, Phil G. wrote:<blockquote class="gmail_quote" style="margin:0;margin-left:0.8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div>Dear Matt,</div><div><br></div><div>thank you for your reply and good suggestions. Now I have let different LiNbO3 slab systems to be calculated:</div><div><br></div><div>a) 14 trilayer system as from Sanna et al., <i>Appl. Surf. Sci.</i> <b>301</b> (2014), 70-78 with Nb-O3-Li2 surface termination on the one side of the slab and Li-O surface termination on the other side. Vacuum space of at least 40 Angstroms was included. The bulk region was already geometry-optimized and bulk atoms were fixed in the inner 6 trilayers. Geometry optimization on the whole slab system was performed and then the pdos of the system was calculated and plotted for every atom layers.<br></div><div>Result: E_F = 0.1552 eV (fermi energy is overall constant, in every atom layers)<br></div><div><br></div><div>b) the same as a), but the bulk region was not already geometry-optimized before. Geometry optimization was performed and calculation of pdos.</div><div>Result: E_F = - 0.8516 eV</div><div><br></div><div>c) the same as b), but 26 trilayers instead of 14 trilayers. Geometry optimization and calculation of pdos were performed.</div><div>Result: E_F = 2.3372 eV</div><div><br></div><div><br></div><div>So, I am wondering why these values differ so much. Should I need band structure calculation of the bulk LiNbO3 in order to find the global valence band edge maximum (with KPOINT calculation)?</div><div><br></div><div>Kind regards,</div><div><br></div><div>Phil</div><div><br></div><br>Am Freitag, 14. Dezember 2018 17:41:03 UTC+1 schrieb Matt W:<blockquote class="gmail_quote" style="margin:0;margin-left:0.8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">In a periodic system the zero of the one electron levels is arbitrary. If you need a reference you need to run a slab calculation with vacuum or try to align semi-core states to something.<div><br></div><div>Matt<br><br>On Friday, December 14, 2018 at 4:33:13 PM UTC, Phil G. wrote:<blockquote class="gmail_quote" style="margin:0;margin-left:0.8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div>Dear people and experts of CP2K,</div><div><br></div><div>after the geometry optimization of the lithium niobate (LiNbO3) unit cell I would like to obtain pdos in order to determine the band gap and Fermi energy of the bulk system.</div><div>After the calculation with ENERGY_FORCE I got pdos files of the three atoms (indexing depends on the z-position of the atoms) and I'm wondering about the value of Fermi energy: E_F = 0.300174 a.u. which is 8.168 eV. Is that not too high? And which energy has the value 0 and what is the reference? What is the Fermi energy defined in the language of CP2K?</div><div>The energy band gap (HOMO-LUMO gap) of 3.62 eV agrees well with experimental values of 3.7 to 3.9 eV. But I cannot imagine that Fermi level has too high energy values.</div><div><br></div><div>Has anyone an idea what is the reason for such high Fermi energy values?<br></div><div><br></div><div>Here the input and output files are attached here.</div><div><br></div><div>Kind regards,</div><div><br></div><div>Phil<br></div></div></blockquote></div></div></blockquote></div></blockquote></div></div></blockquote></div></blockquote></div>