mirror of https://gitlab.com/QEF/q-e.git
110 lines
3.2 KiB
Fortran
110 lines
3.2 KiB
Fortran
!
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! Copyright (C) 2001 PWSCF group
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! This file is distributed under the terms of the
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! GNU General Public License. See the file `License'
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! in the root directory of the present distribution,
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! or http://www.gnu.org/copyleft/gpl.txt .
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!
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!
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!-----------------------------------------------------------------------
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SUBROUTINE polariz_vdw ( iu )
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!-----------------------------------------------------------------------
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!
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! calculates the frequency dependent polarizability
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!
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USE io_global, ONLY : stdout
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USE io_files, ONLY : iunigk
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USE pwcom
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USE kinds, ONLY : DP
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USE phcom
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USE cell_base, ONLY : omega
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USE symme, ONLY : symmatrix, crys_to_cart
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USE eff_v, ONLY : nelecr, veff, et_c, dvext, dpsi_eff
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USE mp_global, ONLY : intra_pool_comm, inter_pool_comm
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USE mp, ONLY : mp_sum
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IMPLICIT NONE
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!
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! I/O variables
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!
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real(kind=DP) :: iu
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!
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! local variables
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!
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INTEGER :: ibnd, ipol, jpol, nrec, ik
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! counter on polarizations
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! counter on records
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! counter on k points
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real(kind=DP) :: w, weight
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COMPLEX(kind=DP) :: zdotc
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CALL start_clock ('polariz')
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epsilon(:,:) = 0.d0
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IF (nksq > 1) REWIND (unit = iunigk)
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DO ik = 1, nksq
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! if (nksq > 1) read (iunigk) npw, igk
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weight = nelecr !wk (ik)
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w = fpi * weight / omega
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DO ipol = 1, 3
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! nrec = (ipol - 1) * nksq + ik
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! call davcio (dvpsi, lrebar, iuebar, nrec, - 1)
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DO jpol = 1, 3
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! nrec = (jpol - 1) * nksq + ik
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! call davcio (dpsi, lrdwf, iudwf, nrec, - 1)
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DO ibnd = 1, nbnd_occ (ik)
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!
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! this is the real part of <DeltaV*psi(E)|DeltaPsi(E)>
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!
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epsilon(ipol,jpol)=epsilon(ipol,jpol)-4.d0*w*REAL( &
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zdotc (npw, dvext (1, ipol, ibnd), 1, dpsi_eff (1, jpol, ibnd), 1) )
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ENDDO
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ENDDO
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ENDDO
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ENDDO
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#ifdef __PARA
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CALL mp_sum ( epsilon, intra_pool_comm )
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CALL mp_sum ( epsilon, inter_pool_comm )
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#endif
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!
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! symmetrize
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!
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! WRITE( stdout,'(/,10x,"Unsymmetrized in crystal axis ",/)')
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! WRITE( stdout,'(10x,"(",3f15.5," )")') ((epsilon(ipol,jpol),
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! + ipol=1,3),jpol=1,3)
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CALL crys_to_cart (epsilon)
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CALL symmatrix (epsilon)
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!
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! pass to cartesian axis
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!
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! WRITE( stdout,'(/,10x,"Symmetrized in cartisian axis ",/)')
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! WRITE( stdout,'(10x,"(",3f15.5," )")') ((epsilon(ipol,jpol),
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! + ipol=1,3),jpol=1,3)
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!
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! add the diagonal part
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!
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DO ipol = 1, 3
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epsilon (ipol, ipol) = epsilon (ipol, ipol) + 1.d0
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ENDDO
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!
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! compute the polarization
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!
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DO ipol = 1, 3
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DO jpol = 1, 3
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IF ( epsilon (ipol, jpol) > 1d-5) &
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epsilon (ipol, jpol) = (3.d0*omega/fpi) * ( epsilon (ipol, jpol) - 1.d0 ) / &
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( epsilon (ipol, jpol) + 2.d0 )
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ENDDO
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ENDDO
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!
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! and print the result
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!
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WRITE( stdout, '(/,10x,"Polarizability in cartesian axis at frequency ",f5.2,/)') iu
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WRITE( stdout, '(10x,"(",3f18.9," )")') ((epsilon(ipol,jpol), ipol=1,3), jpol=1,3)
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CALL stop_clock ('polariz')
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RETURN
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END SUBROUTINE polariz_vdw
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