TABLE OF CONTENTS

ABINIT/eigen_meandege [ Functions ]

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NAME

 eigen_meandege

FUNCTION

 This routine takes the mean values of the responses
 for the eigenstates that are degenerate in energy.

COPYRIGHT

 Copyright (C) 2011-2018 ABINIT group (XG)
 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 .

INPUTS

  eigenresp((3-option)*mband**(3-option)*nkpt*nsppol)= input eigenresp
       eigenrep(2*mband**2*nkpt*nsppol) for first-order derivatives of the eigenvalues
       eigenrep(mband*nkpt*nsppol) for Fan or Debye-Waller second-order derivatives of the eigenvalues
  mband= maximum number of bands
  natom= number of atoms in the unit cell
  nkpt= number of k-points
  nsppol= 1 for unpolarized, 2 for spin-polarized
  option= 1 for eigen(1), 2 for eigen(2) - Fan or Debye-Waller

OUTPUT

  eigenresp_mean(mband*nkpt*nsppol)= eigenresp, averaged over degenerate states

PARENTS

      dfpt_looppert,respfn

CHILDREN

SOURCE

 37 #if defined HAVE_CONFIG_H
 38 #include "config.h"
 39 #endif
 40 
 41 #include "abi_common.h"
 42 
 43 
 44 subroutine eigen_meandege(eigen0,eigenresp,eigenresp_mean,mband,nband,nkpt,nsppol,option)
 45 
 46  use defs_basis
 47  use m_profiling_abi
 48  use m_errors
 49 
 50 !This section has been created automatically by the script Abilint (TD).
 51 !Do not modify the following lines by hand.
 52 #undef ABI_FUNC
 53 #define ABI_FUNC 'eigen_meandege'
 54 !End of the abilint section
 55 
 56  implicit none
 57 
 58 !Arguments ------------------------------------
 59 !scalars
 60  integer,intent(in) :: mband,nkpt,nsppol,option
 61  integer,intent(in) :: nband(nkpt*nsppol)
 62 
 63 !arrays
 64  real(dp),intent(in) :: eigen0(mband*nkpt*nsppol)
 65  real(dp),intent(in) :: eigenresp((3-option)*mband**(3-option)*nkpt*nsppol)
 66  real(dp),intent(out) :: eigenresp_mean(mband*nkpt*nsppol)
 67 
 68 !Local variables-------------------------------
 69 !scalars
 70  integer :: bdtot_index,bd2tot_index,iband,ii,ikpt,isppol,nband_k
 71  real(dp) :: eig0,mean
 72  character(len=500) :: message
 73 !arrays
 74 
 75 ! *********************************************************************
 76 
 77 !DEBUG
 78 !write(std_out,*)' eigen_meandege : enter '
 79 !ENDDEBUG
 80 
 81  if(option/=1 .and. option/=2)then
 82    write(message, '(a,i0)' )' The argument option should be 1 or 2, while it is found that option=',option
 83    MSG_BUG(message)
 84  end if
 85 
 86  bdtot_index=0 ; bd2tot_index=0
 87  do isppol=1,nsppol
 88    do ikpt=1,nkpt
 89      nband_k=nband(ikpt+(isppol-1)*nkpt)
 90      if(option==1)then
 91        do iband=1,nband_k
 92          eigenresp_mean(iband+bdtot_index)=&
 93 &         eigenresp(2*iband-1 + (iband-1)*2*nband_k + bd2tot_index)
 94        end do
 95      else if(option==2)then
 96        do iband=1,nband_k
 97          eigenresp_mean(iband+bdtot_index)=eigenresp(iband+bdtot_index)
 98        end do
 99      end if
100 
101 !    Treat the case of degeneracies : take the mean of degenerate states
102      if(nband_k>1)then
103        eig0=eigen0(1+bdtot_index)
104        ii=1
105        do iband=2,nband_k
106          if(eigen0(iband+bdtot_index)-eig0<tol8)then
107            ii=ii+1
108          else
109            mean=sum(eigenresp_mean(iband-ii+bdtot_index:iband-1+bdtot_index))/ii
110            eigenresp_mean(iband-ii+bdtot_index:iband-1+bdtot_index)=mean
111            ii=1
112          end if
113          eig0=eigen0(iband+bdtot_index)
114          if(iband==nband_k)then
115            mean=sum(eigenresp_mean(iband-ii+1+bdtot_index:iband+bdtot_index))/ii
116            eigenresp_mean(iband-ii+1+bdtot_index:iband+bdtot_index)=mean
117          end if
118        end do
119      end if
120 
121      bdtot_index=bdtot_index+nband_k
122      bd2tot_index=bd2tot_index+2*nband_k**2
123    end do
124  end do
125  
126 !DEBUG
127 !write(std_out,*)' eigen_meandege : exit'
128 !ENDDEBUG
129 
130 end subroutine eigen_meandege