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ABINIT/ep_ph_weights [ Functions ]

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NAME

 ep_ph_weights

FUNCTION

 This routine calculates the phonon integration weights
  for the electron phonon routines, by different methods
    1) Gaussian smearing
    0) Tetrahedron method

COPYRIGHT

 Copyright (C) 2010-2018 ABINIT group (MVer,BXu)
 This file is distributed under the terms of the
 GNU General Public Licence, see ~abinit/COPYING
 or http://www.gnu.org/copyleft/gpl.txt .
 For the initials of contributors, see ~abinit/doc/developers/contributors.txt .

INPUTS

   phfrq = phonon energies
   elphsmear = smearing width for Gaussian method
   omega = input phonon energy
   gprimd = Reciprocal lattice vectors (dimensionful)
   kptrlatt = k-point grid vectors (if divided by determinant of present matrix)
   telphint = option for FS integration:
      0 Tetrahedron method
      1 Gaussian smearing
   k_obj%nkpt = number of FS k-points
   k_obj%kpt = FS k-points
   k_obj%full2full = mapping of FS k-points in full grid under symops

OUTPUT

   tmp_wtq = integration weights

TODO

   weights should be recalculated on-the-fly! The present implementation is not flexible!

PARENTS

      get_tau_k,mka2f,mka2f_tr

CHILDREN

      destroy_tetra,get_tetra_weight,init_tetra,matr3inv

SOURCE

 47 #if defined HAVE_CONFIG_H
 48 #include "config.h"
 49 #endif
 50 
 51 #include "abi_common.h"
 52 
 53 subroutine ep_ph_weights(phfrq,elphsmear,omega_min,omega_max,nomega,gprimd,kptrlatt,nbranch,telphint,k_obj,tmp_wtq)
 54 
 55  use defs_basis
 56  use defs_elphon
 57  use m_profiling_abi
 58  use m_errors
 59  use m_tetrahedron
 60  use m_xmpi
 61 
 62 !This section has been created automatically by the script Abilint (TD).
 63 !Do not modify the following lines by hand.
 64 #undef ABI_FUNC
 65 #define ABI_FUNC 'ep_ph_weights'
 66  use interfaces_32_util
 67 !End of the abilint section
 68 
 69  implicit none
 70 
 71 !Arguments ------------------------------------
 72 !scalars
 73  type(elph_kgrid_type), intent(inout) :: k_obj
 74  integer,intent(in) :: nbranch
 75  real(dp), intent(in) :: elphsmear
 76  real(dp), intent(in) :: omega_min,omega_max
 77  real(dp), intent(in) :: gprimd(3,3)
 78  integer, intent(in) :: kptrlatt(3,3)
 79  integer, intent(in) :: nomega
 80  integer, intent(in) :: telphint
 81 
 82 ! arrays
 83  real(dp), intent(in) :: phfrq(nbranch,k_obj%nkpt)
 84  real(dp), intent(out) :: tmp_wtq(nbranch,k_obj%nkpt,nomega)
 85 
 86 !Local variables-------------------------------
 87 !scalars
 88  integer,parameter :: bcorr0=0
 89  integer :: ikpt, ib1, ibranch
 90  integer :: ierr, iomega
 91  real(dp) :: rcvol, max_occ
 92  real(dp) :: smdeltaprefactor, smdeltafactor, xx, gaussmaxarg
 93  real(dp) :: domega,omega
 94 
 95 ! arrays
 96  real(dp) :: rlatt(3,3), klatt(3,3)
 97  real(dp), allocatable :: tweight(:,:), dtweightde(:,:)
 98  character (len=80) :: errstr
 99  type(t_tetrahedron) :: tetrahedra
100 
101 ! *************************************************************************
102 
103  !write(std_out,*) 'ep_ph : nqpt ', k_obj%nkpt
104 !===================================
105 !Set up integration weights for FS
106 !===================================
107  max_occ = one
108  gaussmaxarg = sqrt(-log(1.d-100))
109  domega = (omega_max - omega_min)/(nomega - 1)
110 
111  if (telphint == 0) then
112 
113 !  =========================
114 !  Tetrahedron integration
115 !  =========================
116 
117    rlatt(:,:) = kptrlatt(:,:)
118    call matr3inv(rlatt,klatt)
119 
120    call init_tetra(k_obj%full2full(1,1,:), gprimd,klatt,k_obj%kpt, k_obj%nkpt,&
121 &   tetrahedra, ierr, errstr)
122    ABI_CHECK(ierr==0,errstr)
123 
124    rcvol = abs (gprimd(1,1)*(gprimd(2,2)*gprimd(3,3)-gprimd(3,2)*gprimd(2,3)) &
125 &   -gprimd(2,1)*(gprimd(1,2)*gprimd(3,3)-gprimd(3,2)*gprimd(1,3)) &
126 &   +gprimd(3,1)*(gprimd(1,2)*gprimd(2,3)-gprimd(2,2)*gprimd(1,3)))
127 
128 !  do all the omega points for tetrahedron weight calculation
129 
130    ABI_ALLOCATE(tweight,(k_obj%nkpt,nomega))
131    ABI_ALLOCATE(dtweightde,(k_obj%nkpt,nomega))
132 
133    do ibranch = 1,nbranch
134      call get_tetra_weight(phfrq(ibranch,:),omega_min,omega_max,&
135 &     max_occ,nomega,k_obj%nkpt,tetrahedra,bcorr0,&
136 &     tweight,dtweightde,xmpi_comm_self)
137 
138      tmp_wtq(ibranch,:,:) = dtweightde(:,:)*k_obj%nkpt
139    end do
140    ABI_DEALLOCATE(tweight)
141    ABI_DEALLOCATE(dtweightde)
142 
143    call destroy_tetra(tetrahedra)
144 
145  else if (telphint == 1) then
146 
147 !  ==============================================================
148 !  Gaussian or integration:
149 !  Each kpt contributes a gaussian of integrated weight 1 
150 !  for each branch. The gaussian being centered at the input energy
151 !  ===============================================================
152 
153 !  took out factor 1/k_obj%nkpt which intervenes only at integration time
154 
155 !  gaussian smdeltaprefactor = sqrt(piinv)/elphsmear/k_obj%nkpt
156    smdeltaprefactor = max_occ*sqrt(piinv)/elphsmear
157    smdeltafactor = one/elphsmear
158 
159    tmp_wtq = zero
160    omega = omega_min
161    do iomega = 1, nomega
162      omega = omega + domega
163      do ikpt=1, k_obj%nkpt
164        do ib1=1,nbranch
165          xx = smdeltafactor*(phfrq(ib1,ikpt)-omega)
166          if (abs(xx) < gaussmaxarg) then
167            tmp_wtq(ib1,ikpt,iomega) = exp(-xx*xx)*smdeltaprefactor
168          end if
169        end do
170      end do
171    end do
172  end if ! if telphint
173 
174 
175 end subroutine ep_ph_weights