! nacl_equil.inp - NVT equilibration of Na+ Cl- in water with the ion pair
! held near contact by a harmonic RESTRAINT on the Na-Cl distance.
! Chapter 15, step 1.  Target versions: CP2K 2023.1 ... 2026.2
!
! Default level is GFN1-xTB (cheap, minutes to hours); -E LEVEL=dft for PBE-D3.
!   mpirun -np 16 cp2k.psmp -i nacl_equil.inp -o nacl_equil_xtb.out
!   bash last_frame.sh nacl_equil_xtb-pos-1.xyz nacl_eq.xyz
! The grid-built start structure is NOT equilibrated: run at least 5 ps here.

@SET LEVEL ${LEVEL-xtb}
@SET COORD ${COORD-nacl_water.xyz}

&GLOBAL
  PROJECT nacl_equil_${LEVEL}
  RUN_TYPE MD
  PRINT_LEVEL LOW
&END GLOBAL

@INCLUDE 'nacl_${LEVEL}_force_eval.inc'

&MOTION
  &MD
    ENSEMBLE NVT
    ! 10000 x 0.5 fs = 5 ps
    STEPS ${STEPS-10000}
    TIMESTEP 0.5
    TEMPERATURE 300.0
    &THERMOSTAT
      TYPE CSVR
      REGION GLOBAL
      &CSVR
        ! short time constant for equilibration (fs)
        TIMECON 50.0
      &END CSVR
    &END THERMOSTAT
  &END MD
  &CONSTRAINT
    ! harmonic restraint K*(d - TARGET)^2 on COLVAR 1 (K in hartree/bohr^2)
    &COLLECTIVE
      COLVAR 1
      INTERMOLECULAR T
      TARGET [angstrom] 2.80
      &RESTRAINT
        K 0.05
      &END RESTRAINT
    &END COLLECTIVE
  &END CONSTRAINT
  &PRINT
    &TRAJECTORY
      FORMAT XYZ
      &EACH
        MD 10
      &END EACH
    &END TRAJECTORY
    &RESTART
      BACKUP_COPIES 0
      &EACH
        MD 100
      &END EACH
    &END RESTART
    &RESTART_HISTORY OFF
    &END RESTART_HISTORY
  &END PRINT
&END MOTION