efld.f90

subroutine efld(nsrc,src,csrc,ntrg,ctrg,ef)
implicit none
! 
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!  "Y88888  "Y88888  "Y8888P"   "Y88888P"   "Y8888P"  888       888  "Y88888P"  
!                                                                              
!
!                             ALL RIGHT RESERVED.                              !
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!  COPYRIGHT (C) 2015 by Filippo Lipparini, Benjamin Stamm, Paolo Gatto        !
!  Eric Cancès, Yvon Maday, Jean-Philip Piquemal, Louis Lagardère and          !
!  Benedetta Mennucci.                                                         !
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!
!
! A modular implementation of COSMO using a domain decomposition linear scaling
! strategy.
!
! This code is governed by the LGPL license and abiding by the rules of 
! distribution of free software.
! This program is distributed in the hope that it will be useful, but  
! WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 
! or FITNESS FOR A PARTICULAR PURPOSE.
! See the GNU Lesser General Public License for more details.
!
! Users of this code are asked to include the following references in their
! publications:
!
! [1] E. Cancès, Y. Maday, B. Stamm
!     "Domain decomposition for implicit solvation models"
!     J. Chem. Phys. 139, 054111 (2013)
!
! [2] F. Lipparini, B. Stamm, E. Cancès, Y. Maday, B. Mennucci
!     "Fast Domain Decomposition Algorithm for Continuum Solvation Models: 
!      Energy and First Derivatives"
!     J. Chem. Theory Comput. 9, 3637–3648 (2013)
!
! Also, include one of the three following reference depending on whether you
! use this code in conjunction with a QM [3], Semiempirical [4] or Classical [5]
! description of the solute:
!
! [3] F. Lipparini, G. Scalmani, L. Lagardère, B. Stamm, E. Cancès, Y. Maday,
!     J.-P. Piquemal, M. J. Frisch, B. Mennucci
!     "Quantum, classical, and hybrid QM/MM calculations in solution: General 
!      implementation of the ddCOSMO linear scaling strategy"
!     J. Chem. Phys. 141, 184108 (2014)
!     (for quantum mechanical models)
!
! [4] F. Lipparini, L. Lagardère, G. Scalmani, B. Stamm, E. Cancès, Y. Maday,
!     J.-P. Piquemal, M. J. Frisch, B. Mennucci
!     "Quantum Calculations in Solution for Large to Very Large Molecules: 
!      A New Linear Scaling QM/Continuum Approach"
!     J. Phys. Chem. Lett. 5, 953-958 (2014)
!     (for semiempirical models)
!
! [5] F. Lipparini, L. Lagardère, C. Raynaud, B. Stamm, E. Cancès, B. Mennucci
!     M. Schnieders, P. Ren, Y. Maday, J.-P. Piquemal
!     "Polarizable Molecular Dynamics in a Polarizable Continuum Solvent"
!     J. Chem. Theory Comput. 11, 623-634 (2015)
!     (for classical models, including polarizable force fields
!     
! The users of this code should also include the appropriate reference to the
! COSMO model. This distribution includes the routines to generate lebedev
! grids by D. Laikov and C. van Wuellen, as publicly available on CCL. If the routines
! are used, the following reference should also be included:
!
! [6] V.I. Lebedev, and D.N. Laikov
!     "A quadrature formula for the sphere of the 131st
!      algebraic order of accuracy"
!     Doklady Mathematics, Vol. 59, No. 3, 1999, pp. 477-481.
!
! Written by Filippo Lipparini, October 2015.
!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!                                                                              !
! computes the electric field produced by the sources src (nsrc point charges  !
! with coordinates csrc) at the ntrg target points ctrg:                       !
!                                                                              !
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!
integer,                    intent(in)    :: nsrc, ntrg
real*8,  dimension(nsrc),   intent(in)    :: src
real*8,  dimension(3,nsrc), intent(in)    :: csrc
real*8,  dimension(3,ntrg), intent(in)    :: ctrg
real*8,  dimension(3,ntrg), intent(inout) :: ef
!
integer :: i, j
real*8  :: dx, dy, dz, r2, rr, r3, f, e(3)
real*8, parameter :: zero=0.0d0
!
ef = zero
!$omp parallel do default(shared) private(j,i,dx,dy,dz,r2,rr,r3,e)
do j = 1, ntrg
  e = zero
  do i = 1, nsrc
    dx   = ctrg(1,j) - csrc(1,i)
    dy   = ctrg(2,j) - csrc(2,i)
    dz   = ctrg(3,j) - csrc(3,i)
    r2   = dx*dx + dy*dy + dz*dz
    rr   = sqrt(r2)
    r3   = r2*rr
    f    = src(i)/r3
    e(1) = e(1) + f*dx
    e(2) = e(2) + f*dy
    e(3) = e(3) + f*dz
  end do
  ef(:,j) = e
end do
return
end