Line data    Source code

       1             : !--------------------------------------------------------------------------------------------------!
       2             : !   CP2K: A general program to perform molecular dynamics simulations                              !
       3             : !   Copyright 2000-2024 CP2K developers group <https://cp2k.org>                                   !
       4             : !                                                                                                  !
       5             : !   SPDX-License-Identifier: GPL-2.0-or-later                                                      !
       6             : !--------------------------------------------------------------------------------------------------!
       7             : 
       8             : ! **************************************************************************************************
       9             : !> \brief given the response wavefunctions obtained by the application
      10             : !>      of the (rxp), p, and ((dk-dl)xp) operators,
      11             : !>      here the current density vector (jx, jy, jz)
      12             : !>      is computed for the 3 directions of the magnetic field (Bx, By, Bz)
      13             : !> \par History
      14             : !>      created 02-2006 [MI]
      15             : !> \author MI
      16             : ! **************************************************************************************************
      17             : MODULE qs_linres_nmr_epr_common_utils
      18             :    USE kinds,                           ONLY: dp
      19             :    USE mathconstants,                   ONLY: gaussi
      20             :    USE pw_grid_types,                   ONLY: pw_grid_type
      21             :    USE pw_methods,                      ONLY: pw_transfer
      22             :    USE pw_pool_types,                   ONLY: pw_pool_type
      23             :    USE pw_types,                        ONLY: pw_c1d_gs_type
      24             : #include "./base/base_uses.f90"
      25             : 
      26             :    IMPLICIT NONE
      27             : 
      28             :    PRIVATE
      29             : 
      30             :    ! *** Public subroutines ***
      31             :    PUBLIC :: mult_G_ov_G2_grid
      32             : 
      33             :    CHARACTER(len=*), PARAMETER, PRIVATE :: moduleN = 'qs_linres_nmr_epr_common_utils'
      34             : 
      35             : CONTAINS
      36             : 
      37             : ! **************************************************************************************************
      38             : !> \brief Given the current density on the PW grid in reciprcal space
      39             : !>       (obtained by FFT), calculate the integral
      40             : !>         \int_{r}[ ((r-r') x j(r))/|r-r'|^3 ] = Bind(r')
      41             : !>       which in reciprcal space reads  (for G/=0)
      42             : !>          i G/|G|^2 x J(G)
      43             : !> \param pw_pool ...
      44             : !> \param rho_gspace ...
      45             : !> \param funcG_times_rho ...
      46             : !> \param idir ...
      47             : !> \param my_chi ...
      48             : !> \author MI
      49             : !> \note
      50             : !>      The G=0 component is not comnputed here, but can be evaluated
      51             : !>      through the susceptibility and added to the shift in a second time
      52             : !>
      53             : !>      This method would not work for a non periodic system
      54             : !>      It should be generalized like the calculation of Hartree
      55             : ! **************************************************************************************************
      56        4500 :    SUBROUTINE mult_G_ov_G2_grid(pw_pool, rho_gspace, funcG_times_rho, idir, my_chi)
      57             : 
      58             :       TYPE(pw_pool_type), POINTER                        :: pw_pool
      59             :       TYPE(pw_c1d_gs_type), INTENT(IN)                   :: rho_gspace
      60             :       TYPE(pw_c1d_gs_type), INTENT(INOUT)                :: funcG_times_rho
      61             :       INTEGER, INTENT(IN)                                :: idir
      62             :       REAL(dp), INTENT(IN)                               :: my_chi
      63             : 
      64             :       INTEGER                                            :: handle, ig, ng
      65             :       REAL(dp)                                           :: g2
      66             :       TYPE(pw_c1d_gs_type)                               :: influence_fn
      67             :       TYPE(pw_grid_type), POINTER                        :: grid
      68             :       CHARACTER(len=*), PARAMETER                        :: routineN = 'mult_G_ov_G2_grid'
      69             : 
      70        4500 :       CALL timeset(routineN, handle)
      71             : 
      72        4500 :       CALL pw_pool%create_pw(influence_fn)
      73             : 
      74        4500 :       grid => influence_fn%pw_grid
      75    87683778 :       DO ig = grid%first_gne0, grid%ngpts_cut_local
      76    87679278 :          g2 = grid%gsq(ig)
      77    87683778 :          influence_fn%array(ig) = gaussi*grid%g(idir, ig)/g2
      78             :       END DO ! ig
      79        4500 :       IF (grid%have_g0) influence_fn%array(1) = 0.0_dp
      80             : 
      81        4500 :       CALL pw_transfer(rho_gspace, funcG_times_rho)
      82             : 
      83        4500 :       ng = SIZE(grid%gsq)
      84    87686028 :       funcG_times_rho%array(1:ng) = funcG_times_rho%array(1:ng)*influence_fn%array(1:ng)
      85        4500 :       IF (grid%have_g0) funcG_times_rho%array(1) = my_chi
      86             : 
      87        4500 :       CALL pw_pool%give_back_pw(influence_fn)
      88             : 
      89        4500 :       CALL timestop(handle)
      90             : 
      91        4500 :    END SUBROUTINE mult_G_ov_G2_grid
      92             : 
      93             : END MODULE qs_linres_nmr_epr_common_utils