!--------------------------------------------------------------------------------------------------!
!   CP2K: A general program to perform molecular dynamics simulations                              !
!   Copyright (C) 2000 - 2017  CP2K developers group                                               !
!--------------------------------------------------------------------------------------------------!

! **************************************************************************************************
!> \brief Set disperson types for DFT calculations
!> \author JGH (04.2014)
! **************************************************************************************************
MODULE qs_dispersion_utils

   USE atomic_kind_types,               ONLY: atomic_kind_type,&
                                              get_atomic_kind
   USE cp_log_handling,                 ONLY: cp_get_default_logger,&
                                              cp_logger_type
   USE cp_output_handling,              ONLY: cp_print_key_finished_output,&
                                              cp_print_key_unit_nr
   USE input_constants,                 ONLY: vdw_nl_DRSLL,&
                                              vdw_nl_LMKLL,&
                                              vdw_nl_RVV10,&
                                              vdw_pairpot_dftd2,&
                                              vdw_pairpot_dftd3,&
                                              vdw_pairpot_dftd3bj,&
                                              xc_vdw_fun_nonloc,&
                                              xc_vdw_fun_pairpot
   USE input_section_types,             ONLY: section_vals_get_subs_vals,&
                                              section_vals_type,&
                                              section_vals_val_get
   USE kinds,                           ONLY: dp
   USE physcon,                         ONLY: bohr,&
                                              kjmol
   USE qs_dispersion_pairpot,           ONLY: qs_scaling_dftd3,&
                                              qs_scaling_dftd3bj,&
                                              qs_scaling_init
   USE qs_dispersion_types,             ONLY: qs_atom_dispersion_type,&
                                              qs_dispersion_type
   USE qs_environment_types,            ONLY: get_qs_env,&
                                              qs_environment_type
   USE qs_kind_types,                   ONLY: get_qs_kind,&
                                              qs_kind_type
#include "./base/base_uses.f90"

   IMPLICIT NONE

   PRIVATE

   CHARACTER(len=*), PARAMETER, PRIVATE :: moduleN = 'qs_dispersion_utils'

   PUBLIC :: qs_dispersion_env_set, qs_write_dispersion

! **************************************************************************************************
CONTAINS
! **************************************************************************************************
!> \brief ...
!> \param dispersion_env ...
!> \param xc_section ...
! **************************************************************************************************
   SUBROUTINE qs_dispersion_env_set(dispersion_env, xc_section)
      TYPE(qs_dispersion_type), POINTER                  :: dispersion_env
      TYPE(section_vals_type), POINTER                   :: xc_section

      CHARACTER(len=*), PARAMETER :: routineN = 'qs_dispersion_env_set', &
         routineP = moduleN//':'//routineN

      LOGICAL                                            :: exfun, explicit
      REAL(dp), POINTER                                  :: params(:), scal(:)
      TYPE(section_vals_type), POINTER                   :: nl_section, pp_section, vdw_section, &
                                                            xc_fun_section

      CPASSERT(ASSOCIATED(dispersion_env))

      ! set general defaults
      dispersion_env%doabc = .FALSE.
      dispersion_env%c9cnst = .FALSE.
      dispersion_env%lrc = .FALSE.
      dispersion_env%srb = .FALSE.
      dispersion_env%verbose = .FALSE.
      NULLIFY (dispersion_env%c6ab, dispersion_env%maxci, dispersion_env%r0ab, dispersion_env%rcov, &
               dispersion_env%r2r4, dispersion_env%cn, dispersion_env%cnkind, dispersion_env%cnlist)
      NULLIFY (dispersion_env%q_mesh, dispersion_env%kernel, dispersion_env%d2phi_dk2, &
               dispersion_env%d2y_dx2)
      NULLIFY (dispersion_env%sab_vdw, dispersion_env%sab_cn)
      NULLIFY (dispersion_env%dftd_section)
      NULLIFY (vdw_section, xc_fun_section)
      vdw_section => section_vals_get_subs_vals(xc_section, "vdw_potential")
      xc_fun_section => section_vals_get_subs_vals(xc_section, "XC_FUNCTIONAL")
      CALL section_vals_val_get(vdw_section, "POTENTIAL_TYPE", i_val=dispersion_env%type)
      IF (dispersion_env%type == xc_vdw_fun_pairpot) THEN
         NULLIFY (pp_section)
         pp_section => section_vals_get_subs_vals(vdw_section, "PAIR_POTENTIAL")
         CALL section_vals_val_get(pp_section, "VERBOSE_OUTPUT", l_val=dispersion_env%verbose)
         CALL section_vals_val_get(pp_section, "TYPE", i_val=dispersion_env%pp_type)
         IF (dispersion_env%pp_type == vdw_pairpot_dftd2) THEN
            ! functional parameters for Grimme D2 type
            CALL section_vals_val_get(pp_section, "EXP_PRE", r_val=dispersion_env%exp_pre)
            CALL section_vals_val_get(pp_section, "SCALING", explicit=explicit)
            IF (.NOT. explicit) THEN
               CALL section_vals_val_get(pp_section, "REFERENCE_FUNCTIONAL", explicit=exfun)
               CPASSERT(exfun)
               CALL qs_scaling_init(dispersion_env%scaling, vdw_section)
            ELSE
               CALL section_vals_val_get(pp_section, "SCALING", r_val=dispersion_env%scaling)
            END IF
         ELSE
            dispersion_env%exp_pre = 0._dp
            dispersion_env%scaling = 0._dp
         END IF
         IF (dispersion_env%pp_type == vdw_pairpot_dftd3 .OR. &
             dispersion_env%pp_type == vdw_pairpot_dftd3bj) THEN
            ! functional parameters for Grimme DFT-D3 type
            CALL section_vals_val_get(pp_section, "EPS_CN", r_val=dispersion_env%eps_cn)
            CALL section_vals_val_get(pp_section, "CALCULATE_C9_TERM", l_val=dispersion_env%doabc)
            CALL section_vals_val_get(pp_section, "REFERENCE_C9_TERM", l_val=dispersion_env%c9cnst)
            CALL section_vals_val_get(pp_section, "LONG_RANGE_CORRECTION", l_val=dispersion_env%lrc)
            CALL section_vals_val_get(pp_section, "SHORT_RANGE_CORRECTION", l_val=dispersion_env%srb)
            IF (dispersion_env%pp_type == vdw_pairpot_dftd3) THEN
               CALL section_vals_val_get(pp_section, "D3_SCALING", explicit=explicit)
            ELSE IF (dispersion_env%pp_type == vdw_pairpot_dftd3bj) THEN
               CALL section_vals_val_get(pp_section, "D3BJ_SCALING", explicit=explicit)
            END IF
            IF (.NOT. explicit) THEN
               CALL section_vals_val_get(pp_section, "REFERENCE_FUNCTIONAL", explicit=exfun)
               CPASSERT(exfun)
               IF (dispersion_env%pp_type == vdw_pairpot_dftd3) THEN
                  CALL qs_scaling_dftd3(dispersion_env%s6, dispersion_env%sr6, dispersion_env%s8, vdw_section)
               ELSE IF (dispersion_env%pp_type == vdw_pairpot_dftd3bj) THEN
                  CALL qs_scaling_dftd3bj(dispersion_env%s6, dispersion_env%a1, dispersion_env%s8, &
                                          dispersion_env%a2, vdw_section)
               END IF
            ELSE
               IF (dispersion_env%pp_type == vdw_pairpot_dftd3) THEN
                  ! zero damping
                  CALL section_vals_val_get(pp_section, "D3_SCALING", r_vals=scal)
                  dispersion_env%s6 = scal(1)
                  dispersion_env%sr6 = scal(2)
                  dispersion_env%s8 = scal(3)
                  dispersion_env%a1 = 0.0_dp
                  dispersion_env%a2 = 0.0_dp
               ELSE IF (dispersion_env%pp_type == vdw_pairpot_dftd3bj) THEN
                  ! BJ damping
                  CALL section_vals_val_get(pp_section, "D3BJ_SCALING", r_vals=scal)
                  dispersion_env%s6 = scal(1)
                  dispersion_env%a1 = scal(2)
                  dispersion_env%s8 = scal(3)
                  dispersion_env%a2 = scal(4)
                  dispersion_env%sr6 = 0.0_dp
               END IF
            END IF
         ELSE
            dispersion_env%s6 = 0._dp
            dispersion_env%sr6 = 0._dp
            dispersion_env%s8 = 0._dp
            dispersion_env%a1 = 0._dp
            dispersion_env%a2 = 0._dp
            dispersion_env%eps_cn = 0._dp
         END IF
         CALL section_vals_val_get(pp_section, "R_CUTOFF", r_val=dispersion_env%rc_disp)
         CALL section_vals_val_get(pp_section, "PARAMETER_FILE_NAME", &
                                   c_val=dispersion_env%parameter_file_name)
         ! set DFTD section for output handling
         dispersion_env%dftd_section => pp_section
      ELSE IF (dispersion_env%type == xc_vdw_fun_nonloc) THEN
         NULLIFY (nl_section)
         nl_section => section_vals_get_subs_vals(vdw_section, "NON_LOCAL")
         CALL section_vals_val_get(nl_section, "VERBOSE_OUTPUT", l_val=dispersion_env%verbose)
         CALL section_vals_val_get(nl_section, "KERNEL_FILE_NAME", &
                                   c_val=dispersion_env%kernel_file_name)
         CALL section_vals_val_get(nl_section, "TYPE", i_val=dispersion_env%nl_type)
         CALL section_vals_val_get(nl_section, "CUTOFF", r_val=dispersion_env%pw_cutoff)
         dispersion_env%pw_cutoff = 0.5_dp*dispersion_env%pw_cutoff
         CALL section_vals_val_get(nl_section, "PARAMETERS", r_vals=params)
         dispersion_env%b_value = params(1)
         dispersion_env%c_value = params(2)
      END IF
   END SUBROUTINE qs_dispersion_env_set

! **************************************************************************************************

! **************************************************************************************************
!> \brief ...
!> \param qs_env ...
!> \param dispersion_env ...
!> \param ounit ...
! **************************************************************************************************
   SUBROUTINE qs_write_dispersion(qs_env, dispersion_env, ounit)
      TYPE(qs_environment_type), POINTER                 :: qs_env
      TYPE(qs_dispersion_type), POINTER                  :: dispersion_env
      INTEGER, INTENT(in), OPTIONAL                      :: ounit

      CHARACTER(LEN=*), PARAMETER :: routineN = 'qs_write_dispersion', &
         routineP = moduleN//':'//routineN

      CHARACTER(LEN=2)                                   :: symbol
      INTEGER                                            :: i, ikind, nkind, output_unit
      TYPE(atomic_kind_type), DIMENSION(:), POINTER      :: atomic_kind_set
      TYPE(cp_logger_type), POINTER                      :: logger
      TYPE(qs_atom_dispersion_type), POINTER             :: disp
      TYPE(qs_kind_type), DIMENSION(:), POINTER          :: qs_kind_set
      TYPE(section_vals_type), POINTER                   :: dft_section

      IF (PRESENT(ounit)) THEN
         output_unit = ounit
      ELSE
         NULLIFY (logger)
         logger => cp_get_default_logger()

         dft_section => section_vals_get_subs_vals(qs_env%input, "DFT")
         output_unit = cp_print_key_unit_nr(logger, dft_section, &
                                            "PRINT%DFT_CONTROL_PARAMETERS", extension=".Log")
      END IF

      IF (output_unit > 0) THEN
         ! vdW type specific output
         IF (dispersion_env%type == xc_vdw_fun_pairpot) THEN
            WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T67,'Pair Potential')")
            ! Pair potentials
            IF (dispersion_env%pp_type == vdw_pairpot_dftd2) THEN
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T35,'Potential Form: S. Grimme, JCC 27: 1787 (2006)')")
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T35,'Cutoff Radius [Bohr]:',T73,F8.2)") dispersion_env%rc_disp
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T35,'Scaling Factor:',T73,F8.4)") dispersion_env%scaling
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T35,'Exp Prefactor for Damping:',T73,F8.1)") dispersion_env%exp_pre
               CALL get_qs_env(qs_env, atomic_kind_set=atomic_kind_set, qs_kind_set=qs_kind_set)
               nkind = SIZE(atomic_kind_set)
               DO ikind = 1, nkind
                  CALL get_atomic_kind(atomic_kind_set(ikind), element_symbol=symbol)
                  CALL get_qs_kind(qs_kind_set(ikind), dispersion=disp)
                  IF (disp%defined) THEN
                     WRITE (output_unit, fmt="(' vdW PARAMETER| ',T18,'Atom=',A2,"// &
                            "T28,'C6[J*nm^6*mol^-1]=',F8.4,T63,'r(vdW)[A]=',F8.4)") &
                        symbol, disp%c6/(1000._dp*bohr**6/kjmol), disp%vdw_radii/bohr
                  ELSE
                     WRITE (output_unit, fmt="(' vdW PARAMETER| ',T20,'Atom=',A2,T70,'not defined')")
                  END IF
               END DO
            ELSE IF (dispersion_env%pp_type == vdw_pairpot_dftd3) THEN
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T26,'DFT-D3 (Version 3.1)')")
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T26,'Potential Form: S. Grimme et al, JCP 132: 154104 (2010)')")
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T26,'Zero Damping')")
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T26,'Cutoff Radius [Bohr]:',T73,F8.2)") dispersion_env%rc_disp
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T26,'s6 Scaling Factor:',T73,F8.4)") dispersion_env%s6
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T26,'sr6 Scaling Factor:',T73,F8.4)") dispersion_env%sr6
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T26,'s8 Scaling Factor:',T73,F8.4)") dispersion_env%s8
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T26,'Cutoff for CN calculation:',T69,E12.4)") dispersion_env%eps_cn
            ELSE IF (dispersion_env%pp_type == vdw_pairpot_dftd3bj) THEN
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T26,'DFT-D3 (Version 3.1)')")
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T26,'Potential Form: S. Grimme et al, JCP 132: 154104 (2010)')")
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T26,'BJ Damping: S. Grimme et al, JCC 32: 1456 (2011)')")
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T26,'Cutoff Radius [Bohr]:',T73,F8.2)") dispersion_env%rc_disp
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T26,'s6 Scaling Factor:',T73,F8.4)") dispersion_env%s6
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T26,'a1 Damping Factor:',T73,F8.4)") dispersion_env%a1
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T26,'s8 Scaling Factor:',T73,F8.4)") dispersion_env%s8
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T26,'a2 Damping Factor:',T73,F8.4)") dispersion_env%a2
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T26,'Cutoff for CN calculation:',T69,E12.4)") dispersion_env%eps_cn
            END IF
         ELSE IF (dispersion_env%type == xc_vdw_fun_nonloc) THEN
            WRITE (output_unit, fmt="(' vdW POTENTIAL| ',T61,'Non-local Functional')")
            WRITE (output_unit, &
                   fmt="(' vdW POTENTIAL| ','Implementation: G. Roman-Perez, J. Soler, PRL 103: 096102 (2009)')")
            WRITE (output_unit, &
                   fmt="(' vdW POTENTIAL| ',T38,' T. Thonhauser et al, PRB 76: 125112 (2007)')")
            WRITE (output_unit, &
                   fmt="(' vdW POTENTIAL| ',T22,' R. Sabatini et al, J.Phys:Condens Matter 24: 424209 (2012)')")
            WRITE (output_unit, &
                   fmt="(' vdW POTENTIAL| ',T16,' Based on QE implementation by Brian Kolb, Timo Thonhauser (2009)')")
            SELECT CASE (dispersion_env%nl_type)
            CASE DEFAULT
               ! unknown functional
               CPABORT("")
            CASE (vdw_nl_DRSLL)
               WRITE (output_unit, &
                      fmt="(' vdW POTENTIAL| ','DRSLL Functional:           M. Dion et al, PRL 92: 246401 (2004)')")
            CASE (vdw_nl_LMKLL)
               WRITE (output_unit, &
                      fmt="(' vdW POTENTIAL| ','LMKLL Functional:            K. Lee et al, PRB 82: 081101 (2010)')")
            CASE (vdw_nl_RVV10)
               WRITE (output_unit, &
                      fmt="(' vdW POTENTIAL| ','RVV10 Functional:    R. Sabatini et al, PRB 87: 041108(R) (2013)')")
            END SELECT
            IF (dispersion_env%verbose) THEN
               WRITE (output_unit, &
                      fmt="(' vdW POTENTIAL| ','         Carrying out vdW-DF run using the following parameters:')")
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ','Nqs =',I8,'        Nr_points =',I8,'       r_max =',F10.3)") &
                  dispersion_env%nqs, dispersion_env%nr_points, dispersion_env%r_max
               WRITE (output_unit, fmt="(' vdW POTENTIAL| ','q_mesh =')")
               WRITE (output_unit, fmt="(8X,4F18.8)") (dispersion_env%q_mesh(i), i=1, dispersion_env%nqs)
               WRITE (output_unit, &
                      fmt="(' vdW POTENTIAL| ','Density cutoff for comvolution:',T68,F10.1,' Ry')") &
                  2.0_dp*dispersion_env%pw_cutoff
            END IF
         END IF
      END IF
      IF (.NOT. PRESENT(ounit)) THEN
         CALL cp_print_key_finished_output(output_unit, logger, dft_section, &
                                           "PRINT%DFT_CONTROL_PARAMETERS")
      END IF

   END SUBROUTINE qs_write_dispersion

! **************************************************************************************************

END MODULE qs_dispersion_utils

