src/rdmdexcdc.f90

   1
   2 ! Copyright (C) 2007-2008 J. K. Dewhurst, S. Sharma and E. K. U. Gross.
   3 ! This file is distributed under the terms of the GNU General Public License.
   4 ! See the file COPYING for license details.
   5
   6 subroutine rdmdexcdc(ikp,evecsv,dedc)
   7 ! calculate the derivative of exchange-correlation energy w.r.t. evecsv
   8 use modmain
   9 implicit none
  10 ! arguments
  11 integer, intent(in) :: ikp
  12 complex(8), intent(in) :: evecsv(nstsv,nstsv)
  13 complex(8), intent(inout) :: dedc(nstsv,nstsv)
  14 ! local variables
  15 integer ik,jk,iv(3)
  16 integer ist1,ist2,ist3,ist4
  17 real(8) t1,t2
  18 ! allocatable arrays
  19 complex(8), allocatable :: vnl(:,:,:,:)
  20 ! external functions
  21 real(8) r3taxi
  22 external r3taxi
  23 if (rdmxctype.eq.0) return
  24 ! calculate the prefactor
  25 if (rdmxctype.eq.1) then
  26   t1=1.d0/occmax
  27 else if (rdmxctype.eq.2) then
  28   if (spinpol) then
  29     t1=1.d0
  30   else
  31     t1=2.d0*(0.25d0)**rdmalpha
  32   end if
  33 else
  34   write(*,*)
  35   write(*,'("Error(rdmdexcdc): rdmxctype not defined : ",I8)') rdmxctype
  36   write(*,*)
  37   stop
  38 end if
  39 allocate(vnl(nstsv,nstsv,nstsv,nkptnr))
  40 ! calculate non-local matrix elements of the type (l-jj-k)
  41 call rdmvnlc(ikp,vnl)
  42 ! start loop over non-reduced k-points
  43 do ik=1,nkptnr
  44 ! copy the matrix elements of the type i-jj-i to vnlrdm
  45   do ist1=1,nstsv
  46     do ist2=1,nstsv
  47       vnlrdm(ist1,ikp,ist2,ik)=dble(vnl(ist1,ist1,ist2,ik))
  48     end do
  49   end do
  50 ! find the equivalent reduced k-point
  51   iv(:)=ivknr(:,ik)
  52   jk=ikmap(iv(1),iv(2),iv(3))
  53   do ist1=1,nstsv
  54     do ist2=1,nstsv
  55       do ist3=1,nstsv
  56         do ist4=1,nstsv
  57           if (rdmxctype.eq.1) then
  58 ! Hartree-Fock functional
  59             t2=t1*occsv(ist3,ikp)*occsv(ist4,jk)
  60           else if (rdmxctype.eq.2) then
  61 ! SDLG functional
  62             t2=t1*(occsv(ist3,ikp)*occsv(ist4,jk))**rdmalpha
  63           end if
  64           dedc(ist2,ist3)=dedc(ist2,ist3)-t2*evecsv(ist2,ist1)* &
  65            vnl(ist1,ist3,ist4,ik)
  66         end do
  67       end do
  68     end do
  69   end do
  70 ! end loop over non-reduced k-points
  71 end do
  72 deallocate(vnl)
  73 return
  74 end subroutine
  75