<div dir="ltr">Dear CP2K users I'm very new to the software and DFT in general. Hope this is the right place to ask this question. I'd like to use CP2K to find structures of solids through geometry optimization runs. I thought that a good strategy for preliminary calculations was to take a known structure (a crystal whose atom positions are known) and run a geometry optimization on it. My hope would be that it is possible to judge the "goodness" of the used parameters by finding a relaxed structure close to the experimental. I tried to work with As2S3 (on a cell counting 8 atoms of As and 12 atoms of S). My first optimization run managed to decrease a lot the energy but completely destroyed the structure of the molecule, to understand what is going on I tried to compute the forces on the atoms in my experimental configuration and it appears that the total force is close to 0, the forces on almost all the atoms are close to 0 except on 2 couples As As and S S where there are enormous (but with 0 resultant) forces. Might this be an anomaly source of the issue? Is there someone that can help me? Did I use bad potentials/basis/xc functional? Not fine enough grids? bad scf algorithms for this system? Thanks in advance. Here it is the cp2k code, I tried to keep it simple, a thing might be useful to know is that without the OT method the SCF run oscillates and apparently doesn't converge. &GLOBAL PROJECT As2S3_forces_calc RUN_TYPE ENERGY_FORCE PRINT_LEVEL LOW &END GLOBAL &FORCE_EVAL METHOD QS &SUBSYS &CELL ABC 11.475 9.577 4.256 ALPHA_BETA_GAMMA 90.0 90.68 90.0 &END CELL &TOPOLOGY COORD_FILE_FORMAT XYZ COORD_FILE_NAME As2S3.xyz &END TOPOLOGY &KIND S BASIS_SET TZV2P-GTH POTENTIAL GTH-PADE &END KIND &KIND As BASIS_SET TZV2P-MOLOPT-SR-GTH POTENTIAL GTH-PADE &END KIND &END SUBSYS &DFT BASIS_SET_FILE_NAME BASIS_MOLOPT_UCL BASIS_SET_FILE_NAME GTH_BASIS_SETS POTENTIAL_FILE_NAME GTH_POTENTIALS &SCF SCF_GUESS RESTART MAX_SCF 500 &OT .TRUE. &END OT &END SCF &XC &XC_FUNCTIONAL PADE &END XC_FUNCTIONAL &END XC &END DFT &PRINT &FORCES ON &END FORCES &END PRINT &END FORCE_EVAL MY_BASIS_SETS is generated by $ cat GTH_BASIS_SETS BASIS_MOLOPT_UCL > MY_BASIS_SET As2S3.xyz: 20 As2S3 (A,B,C)=(11.475 A, 9.577 A, 4.256 A) (alpha,beta,gamma)=(90.0°,90.68°,90.0°) As -2.87968 3.78519 -1.78703 As -6.29671 8.38345 4.62715 As -7.89374 4.70768 1.81738 As -1.28266 7.46095 1.02274 As -4.79404 4.29440 1.17991 As -4.38236 7.87423 1.66021 As -10.88155 5.01715 -0.01930 As 1.70516 7.15148 2.85942 S -4.38840 2.75627 -0.40167 S -4.78799 9.41236 3.24179 S -9.07372 4.85434 3.77704 S -0.10268 7.31429 -0.93692 S -2.91319 3.98145 2.45383 S -6.26321 8.18718 0.38629 S -9.35548 3.43549 0.63482 S 0.17909 8.73314 2.20530 S -0.92786 3.77410 -0.59081 S -8.24854 8.39453 3.43094 S -6.41721 2.99693 2.18326 S -2.75919 9.17170 0.65686 the output (minus the SFC run and the timing informations) (look at atoms 1-2 and 13-14!): DBCSR| Multiplication driver XSMM DBCSR| Multrec recursion limit 512 DBCSR| Multiplication stack size 1000 DBCSR| Maximum elements for images UNLIMITED DBCSR| Multiplicative factor virtual images 1 DBCSR| Randmat seed 12341313 DBCSR| Multiplication size stacks 3 DBCSR| Number of 3D layers SINGLE DBCSR| Use MPI memory allocation T DBCSR| Use RMA algorithm F DBCSR| Use Communication thread T DBCSR| Communication thread load 87 **** **** ****** ** PROGRAM STARTED AT 2016-11-13 18:55:20.125 ***** ** *** *** ** PROGRAM STARTED ON pinco.pallino ** **** ****** PROGRAM STARTED BY fontanar ***** ** ** ** ** PROGRAM PROCESS ID 92218 **** ** ******* ** PROGRAM STARTED IN /home/fontanar/ CP2K| version string: CP2K version 5.0 (Development Version) CP2K| source code revision number: CP2K| cp2kflags: libint fftw3 libxc parallel mpi3 scalapack libxsmm libgrid lib CP2K| deriv_max_am1=6 libint_max_am=8 CP2K| is freely available from https://www.cp2k.org/ CP2K| Program compiled at sam. nov. 5 22:37:09 CET 2016 CP2K| Program compiled on pinco.pallino CP2K| Program compiled for impi CP2K| Data directory path /home/fontanar/cp2k/data CP2K| Input file name As2S3_forces.inp ... ... ... Electronic density on regular grids: -111.9999999385 0.0000000615 Core density on regular grids: 111.9999999829 -0.0000000171 Total charge density on r-space grids: 0.0000000444 Total charge density g-space grids: 0.0000000444 Overlap energy of the core charge distribution: 92.65065405538122 Self energy of the core charge distribution: -398.65263980352455 Core Hamiltonian energy: 105.34301297451202 Hartree energy: 196.75976380751200 Exchange-correlation energy: -41.98461449052979 Total energy: -45.88382345664910 ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.): -45.883823518851351 ATOMIC FORCES in [a.u.] # Atom Kind Element X Y Z 1 1 As -18.30244796 -211.32223506 15.97738109 2 1 As 18.30955215 211.29826724 -15.97476790 3 1 As 0.03033974 -0.01535037 -0.02243601 4 1 As -0.03033573 0.01527827 0.02246948 5 1 As -0.06302510 -0.01399788 -0.06420679 6 1 As 0.06288169 0.01397371 0.06420477 7 1 As -0.14318658 0.03752386 0.05230394 8 1 As 0.14341018 -0.03742549 -0.05230464 9 2 S -0.04378316 -0.00438881 0.05507047 10 2 S 0.04393888 0.00437103 -0.05527078 11 2 S 0.15237734 0.06345576 -0.07781696 12 2 S -0.15250573 -0.06340104 0.07801514 13 2 S 18.35579677 211.32485524 -15.99099261 14 2 S -18.36294583 -211.30098802 15.98856882 15 2 S -0.00508091 -0.11845479 0.09971522 16 2 S 0.00502481 0.11846616 -0.09985495 17 2 S 0.00456838 -0.00974499 0.01222899 18 2 S -0.00470629 0.00972000 -0.01233881 19 2 S 0.00523795 0.02733833 -0.00734223 20 2 S -0.00512153 -0.02726010 0.00737305 SUM OF ATOMIC FORCES -0.00001092 0.00000307 -0.00000070 0.00001136 </div>