! preprocessor_demo.inp - tour of the CP2K input preprocessor
! Tutorial: CP2K chapter 2, section 6.  Works with CP2K 2023.x - 2026.2.
!
! Directives used: @SET, variable expansion, variable with default value,
! @INCLUDE, @IF / @ENDIF, @PRINT.  Needs h2o.xyz and h2o_kinds.inc.
!
!   cp2k.ssmp -e preprocessor_demo.inp                 # show the expanded input
!   cp2k.ssmp -i preprocessor_demo.inp -o demo.out     # default: DZVP, 350 Ry, OT
!   cp2k.ssmp -E BASIS=TZV2P -E CUTOFF=500 -i preprocessor_demo.inp -o demo_tzv2p.out
!   cp2k.ssmp -E USE_OT=0 -i preprocessor_demo.inp -o demo_diag.out
!   cp2k.ssmp -E XC=BLYP -i preprocessor_demo.inp -o demo_xc.out   # no effect, see below
!
! Rules worth remembering:
!  * variables set with @SET in this file OVERRIDE values given with -E/--set;
!    only variables written with a default value can be changed from the
!    command line;
!  * variable names are case sensitive;
!  * do not put trailing comments on @SET lines (the rest of the line is the value).

@SET SYSTEM h2o
@SET XC PBE
@SET BOX 10.0

@PRINT system=${SYSTEM} xc=${XC} basis=${BASIS-DZVP} cutoff=${CUTOFF-350} ot=${USE_OT-1}

&GLOBAL
  PROJECT ${SYSTEM}_${BASIS-DZVP}_c${CUTOFF-350}_ot${USE_OT-1}
  RUN_TYPE ENERGY
  PRINT_LEVEL ${PL-MEDIUM}
&END GLOBAL

&FORCE_EVAL
  METHOD QS
  &DFT
    BASIS_SET_FILE_NAME BASIS_MOLOPT
    POTENTIAL_FILE_NAME GTH_POTENTIALS
    &MGRID
      CUTOFF ${CUTOFF-350}
      REL_CUTOFF 50
    &END MGRID
    &POISSON
      PERIODIC NONE
      POISSON_SOLVER MT
    &END POISSON
    &SCF
      EPS_SCF 1.0E-6
      MAX_SCF 50
      @IF ${USE_OT-1} == 1
      &OT ON
        MINIMIZER DIIS
        PRECONDITIONER FULL_SINGLE_INVERSE
      &END OT
      @ENDIF
    &END SCF
    &XC
      &XC_FUNCTIONAL ${XC}
      &END XC_FUNCTIONAL
    &END XC
  &END DFT
  &SUBSYS
    &CELL
      ABC [angstrom] ${BOX} ${BOX} ${BOX}
      PERIODIC NONE
    &END CELL
    &TOPOLOGY
      COORD_FILE_NAME ${SYSTEM}.xyz
      COORD_FILE_FORMAT XYZ
      &CENTER_COORDINATES
      &END CENTER_COORDINATES
    &END TOPOLOGY
    @INCLUDE 'h2o_kinds.inc'
  &END SUBSYS
&END FORCE_EVAL