<div dir="ltr">Hi Henrique,<div> </div><div>there are several issues with your calculation. I'll try and put up a full how-to on this as it addresses several useful points:</div><div> </div><div>(i) calculating Na+ accurately requires using non-periodic boundary conditions. Set periodic none in &CELL and &POISSON section, along with PSOLVER wavelet</div><div>(ii) you need a larger unit cell to accurately represent NaCl using gamma point only - I used MULTIPLE_UNIT_CELL 4 4 4 (you could use k-points instead)</div><div>(iii) you need a _much_ larger cutoff for Na - 1500 Ry is still not adequate for fully converged stress tensor(!)</div><div> </div><div>To avoid the non cubic optimization you saw, you need to explicitly set SYMMETRY CUBIC in the &CELL section. CP2K doesn't find the symmetry by itself so doesn't keep it.</div><div> </div><div>With these changes I got an enthalpy of ~-990 kJ/mol which is within ~12% of the value you quote with a difference of only ~10 kJ/mol between DZVP and TZV2P basis, so I guess this is likely close to the PBE value. This is a zero K value, not sure about the experimental data. </div><div> </div><div>HTH,</div><div> </div><div>Matt On Sunday, January 6, 2019 at 4:22:52 PM UTC, Henrique Junior wrote:<blockquote class="gmail_quote" style="margin: 0;margin-left: 0.8ex;border-left: 1px #ccc solid;padding-left: 1ex;"><div dir="ltr"> Dear colleagues, For teaching purposes I’m trying to reproduce Born-Haber Cycle energies using CP2K (6.1). Since this is just for didactic purposes, the simplest cases, like NaCl, KBr etc are more than enough, but here is what I’ve got so far: * Starting from .cif files for the solid parts (available online) I have user GEO and CELL Opt to get an optimized energy: &GLOBAL PROJECT NaCl RUN_TYPE CELL_OPT PRINT_LEVEL LOW &END GLOBAL &MOTION &CELL_OPT KEEP_ANGLES true KEEP_SYMMETRY true MAX_ITER 2000 OPTIMIZER BFGS TYPE DIRECT_CELL_OPT EXTERNAL_PRESSURE 10000.0 0.0 0.0 0.0 10000.0 0.0 0.0 0.0 10000.0 PRESSURE_TOLERANCE 10000 &END CELL_OPT &GEO_OPT OPTIMIZER BFGS &END GEO_OPT &END MOTION * For the gaseous parts I have performed only GEO_OPT in a large (fixed) unitary cell. It is interesting to note that despite using KEEP_ANGLES true and KEEP_SYMMETRY true the final cell is not perfectly cubic (why?). Testing for the energy of part of the cycle (NaCl energy is divided by 4, and Cl2 is divided by 2): Na+(g) + ½ Cl2(g) → NaCl(s) (-47.3764756753857 + -14.9639608215114) → -62.3002586417268 Results in -0.04017785517032 Eh or -105.48693988 KJ/mol An energy that is not even close to what is expected (The entire born-haber cycle is attached). So, here is the question: What am I doing wrong? Can the Born-haber cycle energies be obtained using CP2k (maybe with a different approach?)? Thanks in advance for any help Here is the complete input: &GLOBAL PROJECT NaCl RUN_TYPE CELL_OPT PRINT_LEVEL LOW &END GLOBAL &MOTION &CELL_OPT KEEP_ANGLES true KEEP_SYMMETRY true MAX_ITER 20000 OPTIMIZER BFGS TYPE DIRECT_CELL_OPT EXTERNAL_PRESSURE 10000.0 0.0 0.0 0.0 10000.0 0.0 0.0 0.0 10000.0 PRESSURE_TOLERANCE 10000 &END CELL_OPT &GEO_OPT OPTIMIZER BFGS &END GEO_OPT &END MOTION &FORCE_EVAL STRESS_TENSOR DIAGONAL_ANALYTICAL METHOD QS &DFT &QS EPS_DEFAULT 1.0E-12 EXTRAPOLATION ASPC EXTRAPOLATION_ORDER 3 METHOD GPW PW_GRID NS-FULLSPACE MAP_CONSISTENT &END QS CHARGE 0 MULTIPLICITY 1 BASIS_SET_FILE_NAME BASIS POTENTIAL_FILE_NAME POTENTIAL &MGRID COMMENSURATE CUTOFF 600 NGRIDS 5 REALSPACE RELATIVE_CUTOFF 80 &RS_GRID DISTRIBUTION_TYPE AUTOMATIC &END RS_GRID &END MGRID &XC &XC_FUNCTIONAL PBE &END XC_FUNCTIONAL &END XC &SCF EPS_SCF 1.0E-7 MAX_DIIS 4 MAX_SCF 50000 SCF_GUESS RESTART &OT ALGORITHM IRAC ORTHO_IRAC POLY ENERGY_GAP 0.001 LINESEARCH 2PNT MINIMIZER CG PRECONDITIONER FULL_ALL &END OT &OUTER_SCF T EPS_SCF 1.0000000000000000E-07 MAX_SCF 50000 OPTIMIZER DIIS &END OUTER_SCF &END SCF &END DFT &SUBSYS &COORD Na 0.00000000 0.00000000 0.00000000 Na 0.00000000 2.81000000 2.81000000 Na 2.81000000 0.00000000 2.81000000 Na 2.81000000 2.81000000 0.00000000 Cl 2.81000000 2.81000000 2.81000000 Cl 2.81000000 0.00000000 0.00000000 Cl 0.00000000 2.81000000 0.00000000 Cl 0.00000000 0.00000000 2.81000000 &END COORD &KIND Na BASIS_SET DZVP-MOLOPT-SR-GTH-q9 POTENTIAL GTH-PBE-q9 &END KIND &KIND Cl BASIS_SET DZVP-MOLOPT-SR-GTH-q7 POTENTIAL GTH-PBE-q7 &END KIND &CELL ABC 5.62 5.62 5.62 ALPHA_BETA_GAMMA 90.00000 90.00000 90.00000 &END CELL &END SUBSYS &END FORCE_EVAL</div></blockquote></div></div>