mirror of https://gitlab.com/QEF/q-e.git
233 lines
8.3 KiB
Fortran
233 lines
8.3 KiB
Fortran
!
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! Copyright (C) 2004 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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module funct
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IMPLICIT NONE
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PRIVATE
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SAVE
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PUBLIC :: dft, iexch, icorr, igcx, igcc, which_dft
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!
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character (len=20) :: dft
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!
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! dft is the exchange-correlation functional, described by
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! any nonconflicting combination of the following keywords
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! (case-insensitive):
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!
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! Exchange: "nox" none iexch=0
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! "sla" Slater (alpha=2/3) iexch=1 (default)
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! "sl1" Slater (alpha=1.0) iexch=2
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! "rxc" Relativistic Slater iexch=3
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! Correlation: "noc" none icorr=0
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! "pz" Perdew-Zunger icorr=1 (default)
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! "vwn" Vosko-Wilk-Nusair icorr=2
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! "lyp" Lee-Yang-Parr icorr=3
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! "pw" Perdew-Wang icorr=4
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! "wig" Wigner icorr=5
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! "hl" Hedin-Lunqvist icorr=6
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! "obz" Ortiz-Ballone form for PZ icorr=7
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! "obw" Ortiz-Ballone form for PW icorr=8
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! "gl" Gunnarson-Lunqvist icorr=9
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! Gradient Correction on Exchange:
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! "nogx" none igcx =0 (default)
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! "b88" Becke88 (beta=0.0042) igcx =1
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! "ggx" Perdew-Wang 91 igcx =2
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! "pbx" Perdew-Burke-Ernzenhof exch igcx =3
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! "rpb" revised PBE by Zhang-Yang igcx =4
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! "hcth" Cambridge exch, Handy et al igcx =5
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! "optx" Handy's exchange functional igcx =6
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! Gradient Correction on Correlation:
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! "nogc" none igcc =0 (default)
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! "p86" Perdew86 igcc =1
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! "ggc" Perdew-Wang 91 corr. igcc =2
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! "blyp" Lee-Yang-Parr igcc =3
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! "pbx" Perdew-Burke-Ernzenhof corr igcc =4
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! "hcth" Cambridge corr, Handy et al igcc =5
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!
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! Special cases:
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! "bp" = "b88+p86" = Becke-Perdew grad.corr.
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! "pw91" = "pw +ggx+ggc" = PW91 (aka GGA)
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! "blyp" = "sla+b88+lyp+blyp"= BLYP
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! "pbe" = "sla+pw+pbx+pbc" = PBE
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! "revpbe"="sla+pw+rpb+pbc" = revPBE (Zhang-Yang)
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! "hcth" = "nox+noc+hcth+hcth"=HCTH/120
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! "olyp" = "nox+lyp+optx+blyp" !!! UNTESTED !!!
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!
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! References:
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! pz J.P.Perdew and A.Zunger, PRB 23, 5048 (1981)
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! vwn S.H.Vosko, L.Wilk, M.Nusair, Can.J.Phys. 58,1200(1980)
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! pw J.P.Perdew and Y.Wang, PRB 45, 13244 (1992)
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! obpz G.Ortiz and P.Ballone, PRB 50, 1391 (1994)
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! obpw as above
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! b88 A.D.Becke, PRA 38, 3098 (1988)
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! p86 J.P.Perdew, PRB 33, 8822 (1986)
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! pbe J.P.Perdew, K.Burke, M.Ernzerhof, PRL 77, 3865 (1996)
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! pw91 J.P.Perdew and Y. Wang, PRB 46, 6671 (1992)
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! blyp C.Lee, W.Yang, R.G.Parr, PRB 37, 785 (1988)
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! hcth Handy et al, JCP 109, 6264 (1998)
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! olyp Handy et al, JCP 116, 5411 (2002)
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! revPBE Zhang and Yang, PRL 80, 890 (1998)
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integer :: iexch, icorr, igcx, igcc
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!
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! internal indices for exchange-correlation
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! iexch: type of exchange
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! icorr: type of correlation
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! igcx: type of gradient correction on exchange
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! igcc: type of gradient correction on correlations
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! see comments above and routine "which_dft" below
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!
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CONTAINS
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!-----------------------------------------------------------------------
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subroutine which_dft (dft_)
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!-----------------------------------------------------------------------
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!
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! translates a string containing the exchange-correlation name
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! into internal indices iexch, icorr, igcx, igcc
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!
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implicit none
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! input
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character (len=*) :: dft_
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! data
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integer :: nxc, ncc, ngcx, ngcc
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parameter (nxc = 3, ncc = 9, ngcx = 6, ngcc = 5)
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character (len=3) :: exc, corr
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character (len=4) :: gradx, gradc
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dimension exc (0:nxc), corr (0:ncc), gradx (0:ngcx), gradc (0: ngcc)
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! local
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integer :: len, l, i
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integer, parameter:: notset = -1
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character (len=50):: dftout
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logical, external :: matches
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character (len=1), external :: capital
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!
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data exc / 'NOX', 'SLA', 'SL1', 'RXC' /
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data corr / 'NOC', 'PZ', 'VWN', 'LYP', 'PW', 'WIG', 'HL', 'OBZ', &
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'OBW', 'GL' /
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data gradx / 'NOGX', 'B88', 'GGX', 'PBX', 'RPB', 'HCTH','OPTX' /
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data gradc / 'NOGC', 'P86', 'GGC', 'BLYP', 'PBC', 'HCTH'/
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!
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! convert to uppercase
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len = len_trim(dft)
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dftout = ' '
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do l = 1, len
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dftout (l:l) = capital (dft (l:l) )
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enddo
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! exchange
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iexch = notset
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do i = 0, nxc
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if (matches (exc (i), dftout) ) call set_dft_value (iexch, i)
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enddo
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! correlation
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icorr = notset
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do i = 0, ncc
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if (matches (corr (i), dftout) ) call set_dft_value (icorr, i)
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enddo
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! gradient correction, exchange
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igcx = notset
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do i = 0, ngcx
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if (matches (gradx (i), dftout) ) call set_dft_value (igcx, i)
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enddo
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! gradient correction, correlation
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igcc = notset
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do i = 0, ngcc
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if (matches (gradc (i), dftout) ) call set_dft_value (igcc, i)
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enddo
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! special case : BLYP => B88 for gradient correction on exchange
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if (matches ('BLYP', dftout) ) call set_dft_value (igcx, 1)
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! special case : revPBE
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if (matches ('REVPBE', dftout) ) then
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call set_dft_value (icorr,4)
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call set_dft_value (igcx, 4)
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call set_dft_value (igcc, 4)
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else if (matches('RPBE',dftout)) then
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call errore('which_dft', &
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& 'RPBE (Hammer-Hansen-Norskov) not implemented (revPBE is)',1)
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else if (matches ('PBE', dftout) ) then
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! special case : PBE
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call set_dft_value (icorr,4)
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call set_dft_value (igcx, 3)
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call set_dft_value (igcc, 4)
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endif
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! special case : BP = B88 + P86
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if (matches ('BP', dftout) ) then
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call set_dft_value (igcx, 1)
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call set_dft_value (igcc, 1)
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endif
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! special case : PW91 = GGX + GGC
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if (matches ('PW91', dftout) ) then
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call set_dft_value (igcx, 2)
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call set_dft_value (igcc, 2)
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endif
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! special case : HCTH already contains LDA exchange and correlation
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if (matches('HCTH',dftout)) then
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call set_dft_value(iexch,0)
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call set_dft_value(icorr,0)
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end if
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! special case : OPTX already contains LDA exchange
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if (matches('OPTX',dftout)) then
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call set_dft_value(iexch,0)
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end if
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! special case : OLYP = OPTX + LYP
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if (matches('OLYP',dftout)) then
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call set_dft_value(iexch,0)
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call set_dft_value(icorr,3)
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call set_dft_value(igcx,6)
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call set_dft_value(igcc,3)
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end if
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if (igcx == 6) &
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call errore('which_dft','OPTX untested! please test',-igcx)
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! Default value: Slater exchange
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if (iexch == notset) call set_dft_value (iexch, 1)
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! Default value: Perdew-Zunger correlation
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if (icorr == notset) call set_dft_value (icorr, 1)
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! Default value: no gradient correction on exchange
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if (igcx == notset) call set_dft_value (igcx, 0)
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! Default value: no gradient correction on correlation
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if (igcc == notset) call set_dft_value (igcc, 0)
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dftout = exc (iexch) //'-'//corr (icorr) //'-'//gradx (igcx) //'-' &
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&//gradc (igcc)
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! WRITE( stdout,'(a)') dftout
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return
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end subroutine which_dft
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!
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!-----------------------------------------------------------------------
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subroutine set_dft_value (m, i)
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!-----------------------------------------------------------------------
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!
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implicit none
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integer :: m, i
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! local
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integer, parameter :: notset = - 1
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if ( m /= notset .and. m /= i) &
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call errore ('set_dft_value', 'two conflicting matching values', 1)
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m = i
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return
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end subroutine set_dft_value
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end module funct
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