mirror of https://gitlab.com/QEF/q-e.git
130 lines
3.8 KiB
Fortran
130 lines
3.8 KiB
Fortran
!
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! Copyright (C) 2001-2008 Quantum-ESPRESSO 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 dielec()
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!-----------------------------------------------------------------------
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!
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! calculates the dielectric tensor
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!
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#include "f_defs.h"
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USE io_global, ONLY : stdout
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USE io_files, ONLY: iunigk
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USE constants, ONLY: fpi, bohr_radius_angs
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USE cell_base, ONLY: at, bg, omega
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USE klist, ONLY: wk
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USE symme, ONLY: s, nsym
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USE wvfct, ONLY: npw, npwx, igk
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USE noncollin_module, ONLY : npol
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USE kinds, only : DP
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USE efield_mod, ONLY : epsilon
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USE units_ph, ONLY : lrdwf, iudwf, lrebar, iuebar
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USE eqv, ONLY : dpsi, dvpsi
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USE qpoint, ONLY : nksq
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USE control_ph, ONLY : lgamma_gamma, lrpa, lnoloc, nbnd_occ
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USE mp_global, ONLY : inter_pool_comm, intra_pool_comm
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USE mp, ONLY : mp_sum
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implicit none
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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(DP) :: w, weight, chi(3,3)
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complex(DP), external :: ZDOTC
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call start_clock ('dielec')
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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 = 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* DBLE( &
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ZDOTC(npwx*npol, dvpsi (1, ibnd), 1, dpsi (1, 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 symtns (epsilon, nsym, s)
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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 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 trntns (epsilon, at, bg, 1)
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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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! and print the result
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!
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IF (lnoloc) THEN
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WRITE( stdout, '(/,10x,"Dielectric constant in cartesian axis (DV_Hxc=0)",/)')
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ELSE IF (lrpa) THEN
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WRITE( stdout, '(/,10x,"RPA dielectric constant in cartesian axis (DV_xc=0)",/)')
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ELSE
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WRITE( stdout, '(/,10x,"Dielectric constant in cartesian axis ",/)')
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ENDIF
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WRITE( stdout, '(10x,"(",3f18.9," )")') ((epsilon(ipol,jpol), ipol=1,3), jpol=1,3)
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IF (lgamma_gamma) THEN
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!
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! The system is probably a molecule. Try to estimate the polarizability
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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 (ipol == jpol) THEN
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chi(ipol,jpol) = (epsilon(ipol,jpol)-1.0_DP)*omega/fpi
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ELSE
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chi(ipol,jpol) = epsilon(ipol,jpol)*omega/fpi
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END IF
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END DO
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END DO
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WRITE(stdout,'(/5x,"Polarizability (a.u.)^3",20x,"polarizability (A^3)")')
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WRITE(stdout,'(3f10.2,5x,3f14.4)') ( (chi(ipol,jpol), jpol=1,3), &
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(chi(ipol,jpol)*BOHR_RADIUS_ANGS**3, jpol=1,3), ipol=1,3)
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ENDIF
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call stop_clock ('dielec')
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return
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end subroutine dielec
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