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! ---
! Copyright (C) 1996-2016 The SIESTA group
! This file is distributed under the terms of the
! GNU General Public License: see COPYING in the top directory
! or http://www.gnu.org/copyleft/gpl.txt .
! See Docs/Contributors.txt for a list of contributors.
! ---
module metaforce
use precision, only : dp
implicit none
integer, save :: maxGauss = 100
integer, save :: nGauss = 0
logical, save :: lMetaForce
integer, pointer, save :: nGaussPtr(:,:)
real(dp), pointer, save :: GaussK(:)
real(dp), pointer, save :: GaussR0(:)
real(dp), pointer, save :: GaussZeta(:)
CONTAINS
subroutine initmeta()
C
C Reads data for metadynamics Gaussians
C
C Julian Gale, NRI, Curtin University, Feb. 2006
C
use parallel, only : Node
use alloc, only : re_alloc
use sys, only : die
use fdf
implicit none
integer :: k
integer :: ni
integer :: nr
type(block_fdf) :: bfdf
type(parsed_line), pointer :: pline
C Find if there are any Gaussians specified
lMetaForce = fdf_defined('MetaForce')
if (lMetaForce) then
C Allocate arrays for Gaussian data
call re_alloc( nGaussPtr, 1, 2, 1, maxGauss, 'nGaussPtr',
& 'initmeta' )
call re_alloc( GaussK, 1, maxGauss, 'GaussK', 'initmeta' )
call re_alloc( GaussR0, 1, maxGauss, 'GaussR0', 'initmeta' )
call re_alloc( GaussZeta, 1, maxGauss, 'GaussZeta', 'initmeta' )
C Read Gaussians from block
lMetaForce = fdf_block('MetaForce',bfdf)
do k= 1, maxGauss
C Read and parse data line
if (.not. fdf_bline(bfdf,pline))
. call die('initmeta: ERROR in MetaForce block')
ni = fdf_bnintegers(pline)
nr = fdf_bnreals(pline)
C Check that correct info is given
if ((ni .ge. 2) .and. (nr .ge. 3)) then
nGauss = nGauss + 1
nGaussPtr(1,nGauss) = abs(fdf_bintegers(pline,1))
nGaussPtr(2,nGauss) = abs(fdf_bintegers(pline,2))
GaussK(nGauss) = fdf_breals(pline,1)
GaussR0(nGauss) = fdf_breals(pline,2)/0.529177_dp
GaussZeta(nGauss) = fdf_breals(pline,3)
endif
enddo
endif
end subroutine initmeta
subroutine meta(xa,na,ucell,Emeta,fa,stress,forces,stresses)
implicit none
C
C Compute energy and forces due to Gaussians
C
C Julian Gale, NRI, Curtin University, Feb. 2006
C
C Passed variables
integer, intent(in) :: na
logical, intent(in) :: forces
logical, intent(in) :: stresses
real(dp), intent(in) :: ucell(3,3)
real(dp), intent(in) :: xa(3,na)
real(dp), intent(out) :: Emeta
real(dp), intent(inout) :: fa(3,na)
real(dp), intent(inout) :: stress(3,3)
C Local variables
integer :: ii
integer :: i
integer :: j
integer :: k
integer :: ixcell(27)
integer :: iycell(27)
integer :: izcell(27)
real(dp) :: dtrm
real(dp) :: exptrm
real(dp) :: r
real(dp) :: r2
real(dp) :: r2min
real(dp) :: rvol
real(dp) :: vol
real(dp) :: volcel
real(dp) :: x
real(dp) :: y
real(dp) :: z
real(dp) :: xc
real(dp) :: yc
real(dp) :: zc
real(dp) :: xmin
real(dp) :: ymin
real(dp) :: zmin
real(dp) :: xcell(27)
real(dp) :: ycell(27)
real(dp) :: zcell(27)
if (stresses) then
vol = volcel(ucell)
rvol = 1.0_dp/vol
endif
C Initialise energy
Emeta = 0.0_dp
C Find cell images
call cellimagelist(ucell,xcell,ycell,zcell,ixcell,iycell,izcell)
C Loop over Gaussians
do k = 1,nGauss
C Set pointers to atoms
i = nGaussPtr(1,k)
j = nGaussPtr(2,k)
C Set initial coordinates
x = xa(1,j) - xa(1,i)
y = xa(2,j) - xa(2,i)
z = xa(3,j) - xa(3,i)
C Get coordinates of nearest image
r2min = 100000.0_dp
do ii = 1,27
xc = x + xcell(ii)
yc = y + ycell(ii)
zc = z + zcell(ii)
C Compute distance
r2 = xc*xc + yc*yc + zc*zc
if (r2.lt.r2min) then
r2min = r2
xmin = xc
ymin = yc
zmin = zc
endif
enddo
r = sqrt(r2min)
C Compute energy and forces
exptrm = exp(-GaussZeta(k)*(r - GaussR0(k))**2)
Emeta = Emeta + 0.5_dp*GaussK(k)*exptrm
dtrm = GaussK(k)*exptrm*GaussZeta(k)*(r - GaussR0(k))/r
if (forces) then
fa(1,i) = fa(1,i) - dtrm*xmin
fa(2,i) = fa(2,i) - dtrm*ymin
fa(3,i) = fa(3,i) - dtrm*zmin
fa(1,j) = fa(1,j) + dtrm*xmin
fa(2,j) = fa(2,j) + dtrm*ymin
fa(3,j) = fa(3,j) + dtrm*zmin
endif
if (stresses) then
dtrm = dtrm*rvol
stress(1,1) = stress(1,1) + dtrm*xmin*xmin
stress(2,1) = stress(2,1) + dtrm*ymin*xmin
stress(3,1) = stress(3,1) + dtrm*zmin*xmin
stress(1,2) = stress(1,2) + dtrm*xmin*ymin
stress(2,2) = stress(2,2) + dtrm*ymin*ymin
stress(3,2) = stress(3,2) + dtrm*zmin*ymin
stress(1,3) = stress(1,3) + dtrm*xmin*zmin
stress(2,3) = stress(2,3) + dtrm*ymin*zmin
stress(3,3) = stress(3,3) + dtrm*zmin*zmin
endif
enddo
end subroutine meta
end module metaforce
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