<div dir="ltr"><div><div>Hi all, </div> I am trying to optimize (cell and geometry) water box (taken from cp2k benchmarks) with 128 water molecules using DFTB method. I am taking initially 20 20 20 as cell dimensions and asking to minimize cell and geometry simultaneously. I think it is well known that the dimensions should be around 15 ang (In the benchmark study given as 15.6404 15.6404 15.6404). I am getting the dimensions 12.539 12.539 12.539 from my calculations. The input and end of output given here. Why DFTB is far away from the benchmark study? Am I missing something in my input? I really thankful to them, if someone help in this regard. </div><div>I look forward to hear the solutions </div><div>Thanks in advance </div><div>Nagaprasad </div><div> </div>Input: &FORCE_EVAL METHOD Quickstep STRESS_TENSOR ANALYTICAL &DFT &POISSON PERIODIC XYZ &EWALD EWALD_TYPE SPME GMAX 25 O_SPLINE 5 &END EWALD &END POISSON &LOCALIZE ON &PRINT &TOTAL_DIPOLE COMMON_ITERATION_LEVELS 40000 FILENAME ./TOTAL_DIPOLE.dat ADD_LAST NUMERIC PERIODIC TRUE REFERENCE COAC &EACH MD 1 &END EACH &END TOTAL_DIPOLE &END PRINT &END LOCALIZE &QS METHOD DFTB &DFTB DIAGONAL_DFTB3 T SELF_CONSISTENT T HB_SR_GAMMA T DO_EWALD T DISPERSION T &PARAMETER PARAM_FILE_PATH /opt/cp2k_libint/cp2k/data/DFTB/scc PARAM_FILE_NAME scc_parameter DISPERSION_TYPE D3 DISPERSION_RADIUS 15. COORDINATION_CUTOFF 1.e-4 D3_SCALING 1.0 1.5 1.5 DISPERSION_PARAMETER_FILE /opt/cp2k_libint/cp2k/data/dftd3.dat &END PARAMETER &END DFTB &END QS &SCF SCF_GUESS ATOMIC #RESTART #ATOMIC EPS_SCF 1.0E-7 MAX_SCF 2000 &OT PRECONDITIONER FULL_ALL MINIMIZER DIIS &END &OUTER_SCF OPTIMIZER DIIS MAX_SCF 100 EPS_SCF 1.0E-7 &END OUTER_SCF &END SCF &PRINT &MOMENTS PERIODIC TRUE &EACH MD 1 &END MAX_MOMENT 1 FILENAME =dipolemet.traj &END MOMENTS &MULLIKEN &END MULLIKEN &END PRINT &END DFT &SUBSYS &CELL ABC [angstrom] 20.0000 20.0000 20.0000 SYMMETRY CUBIC PERIODIC XYZ &END &TOPOLOGY COORD_FILE_NAME ./<a href="http://h2o.xyz">h2o.xyz</a> COORDINATE xyz &END &END SUBSYS &END FORCE_EVAL &GLOBAL PRINT_LEVEL MEDIUM PROJECT wat RUN_TYPE CELL_OPT EXTENDED_FFT_LENGTHS &END GLOBAL &MOTION &CELL_OPT EXTERNAL_PRESSURE 1.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 1.0 TYPE DIRECT_CELL_OPT MINIMIZER LBFGS KEEP_SYMMETRY MAX_ITER 5000 &PRINT &CELL ON &EACH CELL_OPT 1 &END EACH &END CELL &END PRINT &END CELL_OPT &PRINT &RESTART LOG_PRINT_KEY T &EACH MD 20 &END EACH ADD_LAST NUMERIC &END RESTART &TRAJECTORY LOG_PRINT_KEY T FORMAT XYZ UNIT angstrom &EACH MD 1 &END EACH ADD_LAST NUMERIC &END TRAJECTORY &VELOCITIES LOG_PRINT_KEY T FORMAT XYZ UNIT angstrom &EACH MD 1 &END EACH ADD_LAST NUMERIC &END VELOCITIES &END PRINT &END MOTION <div> few steps in Output: -------- Informations at step = 1092 ------------ Optimization Method = LBFGS Total Energy = -526.7648934300 Internal Pressure [bar] = 20.7598453579 Real energy change = -0.0000068927 Decrease in energy = YES Used time = 2.757 Convergence check : Max. step size = 0.0024311351 Conv. limit for step size = 0.0030000000 Convergence in step size = YES RMS step size = 0.0005225723 Conv. limit for RMS step = 0.0015000000 Convergence in RMS step = YES Max. gradient = 0.0003651668 Conv. limit for gradients = 0.0004500000 Conv. in gradients = YES RMS gradient = 0.0000715192 Conv. limit for RMS grad. = 0.0003000000 Conv. in RMS gradients = YES Pressure Deviation [bar] = 19.7598453579 Pressure Tolerance [bar] = 100.0000000000 Conv. for PRESSURE = YES --------------------------------------------------- ******************************************************************************* *** GEOMETRY OPTIMIZATION COMPLETED *** ******************************************************************************* 17:54:28 NOTE in cp_output_handling:cp_print_key_unit_nr :: Moving file wat-1.restart.bak-2 into file wat-1.restart.bak-3. 17:54:28 NOTE in cp_output_handling:cp_print_key_unit_nr :: Moving file wat-1.restart.bak-1 into file wat-1.restart.bak-2. 17:54:28 NOTE in cp_output_handling:cp_print_key_unit_nr :: Moving file wat-1.restart into file wat-1.restart.bak-1. 17:54:28 NOTE in cp_output_handling:cp_print_key_unit_nr :: Writing RESTART 1_1092 to wat-1.restart Reevaluating energy at the minimum CELL| Volume [angstrom^3]: 1971.378 CELL| Vector a [angstrom]: 12.539 0.000 0.000 |a| = 12.539 CELL| Vector b [angstrom]: 0.000 12.539 0.000 |b| = 12.539 CELL| Vector c [angstrom]: 0.000 0.000 12.539 |c| = 12.539 CELL| Angle (b,c), alpha [degree]: 90.000 CELL| Angle (a,c), beta [degree]: 90.000 CELL| Angle (a,b), gamma [degree]: 90.000 CELL| Requested initial symmetry: CUBIC CELL| Numerically orthorhombic: YES DISTRIBUTION OF THE NEIGHBOR LISTS Total number of particle pairs: 31467 Total number of matrix elements: 31467 Average number of particle pairs: 1259 Maximum number of particle pairs: 1354 Average number of matrix element: 1259 Maximum number of matrix elements: 1354 Number of electrons: 1024 Number of occupied orbitals: 512 Number of molecular orbitals: 512 Number of orbital functions: 768 Number of independent orbital functions: 768 Parameters for the always stable predictor-corrector (ASPC) method: ASPC order: 3 </div></div>