./67_common/ionion_realspace.F90

ABINIT/ionion_realspace

ABINIT/ionion_realspace [ Functions ]

NAME

 ionion_realspace

FUNCTION

 Compute the ion/ion interaction energies and forces in real space
 case. Use ewald() instead if computations are done in reciprocal
 space since it also includes the correction for the shift done in
 potentials calculations and includes replica interactions.

 Copyright (C) 1998-2018 ABINIT group (DCA, XG, GMR)
 This file is distributed under the terms of the
 GNU General Public License, see ~abinit/COPYING
 or http://www.gnu.org/copyleft/gpl.txt .
 For the initials of contributors, see ~abinit/doc/developers/contributors.txt .

INPUTS

  dtset <type(dataset_type)>=all input variables in this dataset
  rmet(3,3)=metric tensor in real space (bohr^2)
  xred(3,natom)=relative coords of atoms in unit cell (dimensionless)
  zion(ntypat)=charge on each type of atom (real number)

OUTPUT

  eew=final ion/ion energy in hartrees
  grewtn(3,natom)=grads of ion/ion wrt xred(3,natom), hartrees.

PARENTS

      setvtr

CHILDREN

      xred2xcart

SOURCE

 38 #if defined HAVE_CONFIG_H
 39 #include "config.h"
 40 #endif
 41 
 42 #include "abi_common.h"
 43 
 44 subroutine ionion_realSpace(dtset, eew, grewtn, rprimd, xred, zion)
 45 
 46  use defs_basis
 47  use defs_abitypes
 48  use m_profiling_abi
 49 
 50  use m_geometry,    only : xred2xcart
 51 
 52 !This section has been created automatically by the script Abilint (TD).
 53 !Do not modify the following lines by hand.
 54 #undef ABI_FUNC
 55 #define ABI_FUNC 'ionion_realSpace'
 56 !End of the abilint section
 57 
 58  implicit none
 59 
 60 !Arguments ------------------------------------
 61 !scalars
 62  real(dp),intent(out) :: eew
 63  type(dataset_type),intent(in) :: dtset
 64 !arrays
 65  real(dp),intent(in) :: rprimd(3,3),zion(dtset%ntypat)
 66  real(dp),intent(in) :: xred(3,dtset%natom)
 67  real(dp),intent(out) :: grewtn(3,dtset%natom)
 68 
 69 !Local variables-------------------------------
 70 !scalars
 71  integer :: ia1,ia2,iatom,igeo
 72  real(dp) :: r
 73 !arrays
 74  real(dp),allocatable :: grew_cart(:,:),xcart(:,:)
 75 
 76 ! *************************************************************************
 77 
 78 !Store xcart for each atom
 79  ABI_ALLOCATE(xcart,(3, dtset%natom))
 80  call xred2xcart(dtset%natom, rprimd, xcart, xred)
 81 
 82 !Summing the interaction between ions.
 83  eew = 0._dp
 84  do ia1 = 1, dtset%natom, 1
 85    do ia2 = ia1 + 1, dtset%natom, 1
 86      r = sqrt((xcart(1, ia1) - xcart(1, ia2)) ** 2 + &
 87 &     (xcart(2, ia1) - xcart(2, ia2)) ** 2 + &
 88 &     (xcart(3, ia1) - xcart(3, ia2)) ** 2)
 89      eew = eew + zion(dtset%typat(ia1)) * zion(dtset%typat(ia2)) / r
 90    end do
 91  end do
 92 
 93 !Allocate temporary array to store cartesian gradients.
 94  ABI_ALLOCATE(grew_cart,(3, dtset%natom))
 95 
 96 !Summing the forces for each atom
 97  do ia1 = 1, dtset%natom, 1
 98    grew_cart(:, ia1) = 0._dp
 99    do ia2 = 1, dtset%natom, 1
100      if (ia1 /= ia2) then
101        r = (xcart(1, ia1) - xcart(1, ia2)) ** 2 + &
102 &       (xcart(2, ia1) - xcart(2, ia2)) ** 2 + &
103 &       (xcart(3, ia1) - xcart(3, ia2)) ** 2
104        do igeo = 1, 3, 1
105          grew_cart(igeo, ia1) = grew_cart(igeo, ia1) - (xcart(igeo, ia1) - xcart(igeo, ia2)) * &
106 &         zion(dtset%typat(ia1)) * zion(dtset%typat(ia2)) / (r ** 1.5_dp)
107        end do
108      end if
109    end do
110  end do
111 
112  ABI_DEALLOCATE(xcart)
113 
114 !Transform cartesian gradients to reduced gradients.
115  do iatom = 1, dtset%natom, 1
116    do igeo = 1, 3, 1
117      grewtn(igeo, iatom) = rprimd(1, igeo) * grew_cart(1, iatom) + &
118 &     rprimd(2, igeo) * grew_cart(2, iatom) + &
119 &     rprimd(3, igeo) * grew_cart(3, iatom)
120    end do
121  end do
122  ABI_DEALLOCATE(grew_cart)
123 
124 end subroutine ionion_realSpace

TABLE OF CONTENTS

ABINIT/ionion_realspace [ Functions ]