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1 : !!****m* ABINIT/m_paw_efield
2 : !! NAME
3 : !! m_paw_efield
4 : !!
5 : !! FUNCTION
6 : !! This module contains routines related to the treatment of electric field in the PAW approach.
7 : !!
8 : !! COPYRIGHT
9 : !! Copyright (C) 2018-2026 ABINIT group (FJ, PH)
10 : !! This file is distributed under the terms of the
11 : !! GNU General Public License, see ~abinit/COPYING
12 : !! or http://www.gnu.org/copyleft/gpl.txt .
13 : !!
14 : !! SOURCE
15 :
16 : #if defined HAVE_CONFIG_H
17 : #include "config.h"
18 : #endif
19 :
20 : #include "abi_common.h"
21 :
22 : MODULE m_paw_efield
23 :
24 : use defs_basis
25 : use m_abicore
26 : use m_errors
27 : use m_time, only : timab
28 : use m_xmpi, only : xmpi_sum
29 :
30 : use m_pawtab, only : pawtab_type
31 : use m_pawrhoij, only : pawrhoij_type
32 :
33 : implicit none
34 :
35 : private
36 :
37 : !public procedures.
38 : public :: pawpolev ! Compute the PAW on-site term for polarization
39 :
40 : CONTAINS !========================================================================================
41 : !!***
42 :
43 : !----------------------------------------------------------------------
44 :
45 : !!****f* ABINIT/pawpolev
46 : !! NAME
47 : !! pawpolev
48 : !!
49 : !! FUNCTION
50 : !! Compute the PAW term for polarization, named expected value term
51 : !!
52 : !! COPYRIGHT
53 : !! Copyright (C) 1998-2026 ABINIT group (FJ, PH)
54 : !! This file is distributed under the terms of the
55 : !! GNU General Public License, see ~abinit/COPYING
56 : !! or http://www.gnu.org/copyleft/gpl.txt .
57 : !! For the initials of contributors, see ~abinit/doc/developers/contributors.txt.
58 : !!
59 : !! INPUTS
60 : !! comm_atom=--optional-- MPI communicator over atoms
61 : !! my_natom=number of atoms treated by current processor
62 : !! natom=number of atoms in cell.
63 : !! ntypat = number of atom types
64 : !! pawrhoij(natom) <type(pawrhoij_type)>= paw rhoij occupancies and related data
65 : !! pawtab(ntypat) <type(pawtab_type)>=paw tabulated starting data
66 : !!
67 : !! OUTPUT
68 : !! pelev(3)= electronic polarisation. expectation value term (PAW only)
69 : !!
70 : !! SOURCE
71 :
72 99 : subroutine pawpolev(my_natom,natom,ntypat,pawrhoij,pawtab,pelev,&
73 : & comm_atom) ! optional argument (parallelism)
74 :
75 : !Arguments ---------------------------------------------
76 : !scalars
77 : integer,intent(in) :: my_natom,natom,ntypat
78 : integer,optional,intent(in) :: comm_atom
79 : !arrays
80 : real(dp),intent(out) :: pelev(3)
81 : type(pawrhoij_type),intent(in) :: pawrhoij(my_natom)
82 : type(pawtab_type),intent(in) :: pawtab(ntypat)
83 :
84 :
85 : !Local variables ---------------------------------------
86 : !scalars
87 : integer :: iatom,idir,ierr,irhoij,ispden,itypat,jrhoij,klmn
88 : logical :: paral_atom
89 : real(dp) :: c1,ro_dlt
90 : !arrays
91 : integer,dimension(3) :: idirindx = (/4,2,3/)
92 : real(dp) :: tsec(2)
93 :
94 : ! *************************************************************************
95 :
96 : DBG_ENTER("COLL")
97 :
98 99 : call timab(560,1,tsec)
99 :
100 99 : if (my_natom>0) then
101 99 : ABI_CHECK(pawrhoij(1)%qphase==1,'pawpolev not supposed to be called with qphase/=1!')
102 : end if
103 :
104 : !Check for parallelism over atoms
105 99 : paral_atom=(present(comm_atom).and.(my_natom/=natom))
106 :
107 : !note that when vector r is expanded in real spherical harmonics, the factor
108 : !sqrt(four_pi/three) appears, as in the following
109 : !x = sqrt(four_pi/three)*r*S_{1,1}
110 : !y = sqrt(four_pi/three)*r*S_{1,-1}
111 : !z = sqrt(four_pi/three)*r*S_{1,0}
112 : !
113 : !the moments pawtab()%qijl do not include such normalization factors
114 : !see pawinit.F90 for their definition and computation
115 :
116 99 : c1=sqrt(four_pi/three)
117 :
118 99 : pelev=zero
119 396 : do idir=1,3
120 990 : do iatom=1,my_natom
121 594 : itypat=pawrhoij(iatom)%itypat
122 1485 : do ispden=1,pawrhoij(iatom)%nspden
123 594 : jrhoij=1
124 18741 : do irhoij=1,pawrhoij(iatom)%nrhoijsel
125 17553 : klmn=pawrhoij(iatom)%rhoijselect(irhoij)
126 17553 : ro_dlt=pawrhoij(iatom)%rhoijp(jrhoij,ispden)*pawtab(itypat)%dltij(klmn)
127 17553 : pelev(idir)=pelev(idir)+ro_dlt*c1*pawtab(itypat)%qijl(idirindx(idir),klmn)
128 18147 : jrhoij=jrhoij+pawrhoij(iatom)%cplex_rhoij
129 : end do
130 : end do
131 : end do
132 : end do
133 :
134 99 : if (paral_atom) then
135 0 : call xmpi_sum(pelev,comm_atom,ierr)
136 : end if
137 :
138 99 : call timab(560,2,tsec)
139 :
140 : DBG_EXIT("COLL")
141 :
142 99 : end subroutine pawpolev
143 : !!***
144 :
145 : !----------------------------------------------------------------------
146 :
147 : END MODULE m_paw_efield
148 : !!***
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