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!! Calculates Long Range forces Lennard-Jones interactions. |
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!! Corresponds to the force field defined in lj_FF.cpp |
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!! @author Charles F. Vardeman II |
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!! @author Matthew Meineke |
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!! @version $Id: calc_LJ_FF.F90,v 1.15 2004-01-06 18:54:57 chuckv Exp $, $Date: 2004-01-06 18:54:57 $, $Name: not supported by cvs2svn $, $Revision: 1.15 $ |
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|
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module lj |
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use definitions |
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use atype_module |
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use vector_class |
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use simulation |
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#ifdef IS_MPI |
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use mpiSimulation |
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#endif |
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use force_globals |
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|
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implicit none |
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PRIVATE |
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|
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#define __FORTRAN90 |
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#include "fForceField.h" |
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|
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integer, save :: LJ_Mixing_Policy |
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real(kind=DP), save :: LJ_rcut |
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logical, save :: havePolicy = .false., haveCut = .false. |
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|
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|
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!! Logical has lj force field module been initialized? |
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|
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logical, save :: LJ_FF_initialized = .false. |
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|
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!! Public methods and data |
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public :: init_LJ_FF |
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public :: setCutoffLJ |
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public :: do_lj_pair |
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|
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type :: lj_mixed_params |
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!! Lennard-Jones epsilon |
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real ( kind = dp ) :: epsilon = 0.0_dp |
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!! Lennard-Jones Sigma |
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real ( kind = dp ) :: sigma = 0.0_dp |
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!! Lennard-Jones Sigma to sixth |
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real ( kind = dp ) :: sigma6 = 0.0_dp |
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!! |
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real ( kind = dp ) :: tp6 |
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real ( kind = dp ) :: tp12 |
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|
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real ( kind = dp ) :: delta = 0.0_dp |
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|
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|
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end type lj_mixed_params |
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|
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type (lj_mixed_params), dimension(:,:), pointer :: ljMixed |
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|
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contains |
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|
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subroutine init_LJ_FF(mix_Policy, status) |
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integer, intent(in) :: mix_Policy |
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integer, intent(out) :: status |
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integer :: myStatus |
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|
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if (mix_Policy == LB_MIXING_RULE) then |
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LJ_Mixing_Policy = LB_MIXING_RULE |
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else |
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if (mix_Policy == EXPLICIT_MIXING_RULE) then |
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LJ_Mixing_Policy = EXPLICIT_MIXING_RULE |
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else |
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write(*,*) 'Unknown Mixing Policy!' |
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status = -1 |
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return |
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endif |
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endif |
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|
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havePolicy = .true. |
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|
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if (haveCut) then |
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status = 0 |
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call createMixingList(myStatus) |
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if (myStatus /= 0) then |
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status = -1 |
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return |
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end if |
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|
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LJ_FF_initialized = .true. |
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end if |
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|
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end subroutine init_LJ_FF |
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|
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subroutine setCutoffLJ(rcut, status) |
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integer :: status, myStatus |
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real(kind=dp) :: rcut |
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|
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status = 0 |
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|
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LJ_rcut = rcut |
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haveCut = .true. |
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|
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if (havePolicy) then |
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status = 0 |
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call createMixingList(myStatus) |
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if (myStatus /= 0) then |
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status = -1 |
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return |
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end if |
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|
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LJ_FF_initialized = .true. |
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end if |
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|
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return |
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end subroutine setCutoffLJ |
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|
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subroutine createMixingList(status) |
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integer :: nAtypes |
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integer :: status |
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integer :: i |
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integer :: j |
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real ( kind = dp ) :: mySigma_i,mySigma_j |
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real ( kind = dp ) :: myEpsilon_i,myEpsilon_j |
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real ( kind = dp ) :: rcut6 |
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status = 0 |
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|
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nAtypes = getSize(atypes) |
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if (nAtypes == 0) then |
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status = -1 |
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return |
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end if |
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|
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if (.not. associated(ljMixed)) then |
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allocate(ljMixed(nAtypes, nAtypes)) |
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endif |
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|
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rcut6 = LJ_rcut**6 |
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|
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! This loops through all atypes, even those that don't support LJ forces. |
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do i = 1, nAtypes |
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|
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call getElementProperty(atypes, i, "lj_epsilon", myEpsilon_i) |
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call getElementProperty(atypes, i, "lj_sigma", mySigma_i) |
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! do self mixing rule |
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ljMixed(i,i)%sigma = mySigma_i |
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|
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ljMixed(i,i)%sigma6 = (ljMixed(i,i)%sigma) ** 6 |
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|
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ljMixed(i,i)%tp6 = (ljMixed(i,i)%sigma6)/rcut6 |
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|
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ljMixed(i,i)%tp12 = (ljMixed(i,i)%tp6) ** 2 |
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|
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|
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ljMixed(i,i)%epsilon = myEpsilon_i |
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|
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ljMixed(i,i)%delta = -4.0_DP * ljMixed(i,i)%epsilon * & |
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(ljMixed(i,i)%tp12 - ljMixed(i,i)%tp6) |
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|
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do j = i + 1, nAtypes |
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call getElementProperty(atypes,j,"lj_epsilon",myEpsilon_j) |
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call getElementProperty(atypes,j,"lj_sigma", mySigma_j) |
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|
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ljMixed(i,j)%sigma = & |
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calcLJMix("sigma",mySigma_i, & |
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mySigma_j) |
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|
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ljMixed(i,j)%sigma6 = & |
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(ljMixed(i,j)%sigma)**6 |
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|
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|
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ljMixed(i,j)%tp6 = ljMixed(i,j)%sigma6/rcut6 |
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|
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ljMixed(i,j)%tp12 = (ljMixed(i,j)%tp6) ** 2 |
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|
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|
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ljMixed(i,j)%epsilon = & |
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calcLJMix("epsilon",myEpsilon_i, & |
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myEpsilon_j) |
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|
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ljMixed(i,j)%delta = -4.0_DP * ljMixed(i,j)%epsilon * & |
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(ljMixed(i,j)%tp12 - ljMixed(i,j)%tp6) |
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|
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|
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ljMixed(j,i)%sigma = ljMixed(i,j)%sigma |
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ljMixed(j,i)%sigma6 = ljMixed(i,j)%sigma6 |
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ljMixed(j,i)%tp6 = ljMixed(i,j)%tp6 |
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ljMixed(j,i)%tp12 = ljMixed(i,j)%tp12 |
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ljMixed(j,i)%epsilon = ljMixed(i,j)%epsilon |
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ljMixed(j,i)%delta = ljMixed(i,j)%delta |
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|
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end do |
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end do |
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|
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end subroutine createMixingList |
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|
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subroutine do_lj_pair(atom1, atom2, d, rij, r2, pot, f, do_pot, do_stress) |
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|
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integer, intent(in) :: atom1, atom2 |
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real( kind = dp ), intent(in) :: rij, r2 |
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real( kind = dp ) :: pot |
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real( kind = dp ), dimension(3,nLocal) :: f |
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real( kind = dp ), intent(in), dimension(3) :: d |
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logical, intent(in) :: do_pot, do_stress |
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|
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! local Variables |
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real( kind = dp ) :: drdx, drdy, drdz |
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real( kind = dp ) :: fx, fy, fz |
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real( kind = dp ) :: pot_temp, dudr |
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real( kind = dp ) :: sigma6 |
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real( kind = dp ) :: epsilon |
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real( kind = dp ) :: r6 |
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real( kind = dp ) :: t6 |
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real( kind = dp ) :: t12 |
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real( kind = dp ) :: delta |
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integer :: id1, id2 |
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|
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|
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if (rij.lt.LJ_rcut) then |
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|
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! Look up the correct parameters in the mixing matrix |
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#ifdef IS_MPI |
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sigma6 = ljMixed(atid_Row(atom1),atid_Col(atom2))%sigma6 |
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epsilon = ljMixed(atid_Row(atom1),atid_Col(atom2))%epsilon |
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delta = ljMixed(atid_Row(atom1),atid_Col(atom2))%delta |
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#else |
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sigma6 = ljMixed(atid(atom1),atid(atom2))%sigma6 |
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epsilon = ljMixed(atid(atom1),atid(atom2))%epsilon |
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delta = ljMixed(atid(atom1),atid(atom2))%delta |
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#endif |
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|
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r6 = r2 * r2 * r2 |
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|
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t6 = sigma6/ r6 |
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t12 = t6 * t6 |
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|
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pot_temp = 4.0E0_DP * epsilon * (t12 - t6) + delta |
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|
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dudr = 24.0E0_DP * epsilon * (t6 - 2.0E0_DP*t12) / rij |
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|
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drdx = d(1) / rij |
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drdy = d(2) / rij |
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drdz = d(3) / rij |
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|
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fx = dudr * drdx |
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fy = dudr * drdy |
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fz = dudr * drdz |
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|
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#ifdef IS_MPI |
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if (do_pot) then |
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pot_Row(atom1) = pot_Row(atom1) + pot_temp*0.5 |
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pot_Col(atom2) = pot_Col(atom2) + pot_temp*0.5 |
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endif |
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|
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f_Row(1,atom1) = f_Row(1,atom1) + fx |
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f_Row(2,atom1) = f_Row(2,atom1) + fy |
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f_Row(3,atom1) = f_Row(3,atom1) + fz |
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|
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f_Col(1,atom2) = f_Col(1,atom2) - fx |
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f_Col(2,atom2) = f_Col(2,atom2) - fy |
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f_Col(3,atom2) = f_Col(3,atom2) - fz |
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|
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#else |
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if (do_pot) pot = pot + pot_temp |
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|
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f(1,atom1) = f(1,atom1) + fx |
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f(2,atom1) = f(2,atom1) + fy |
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f(3,atom1) = f(3,atom1) + fz |
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|
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f(1,atom2) = f(1,atom2) - fx |
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f(2,atom2) = f(2,atom2) - fy |
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f(3,atom2) = f(3,atom2) - fz |
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#endif |
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|
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if (do_stress) then |
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|
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#ifdef IS_MPI |
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id1 = tagRow(atom1) |
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id2 = tagColumn(atom2) |
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#else |
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id1 = atom1 |
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id2 = atom2 |
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#endif |
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|
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if (molMembershipList(id1) .ne. molMembershipList(id2)) then |
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|
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! because the d vector is the rj - ri vector, and |
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! because fx, fy, fz are the force on atom i, we need a |
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! negative sign here: |
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|
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tau_Temp(1) = tau_Temp(1) - d(1) * fx |
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tau_Temp(2) = tau_Temp(2) - d(1) * fy |
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tau_Temp(3) = tau_Temp(3) - d(1) * fz |
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tau_Temp(4) = tau_Temp(4) - d(2) * fx |
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tau_Temp(5) = tau_Temp(5) - d(2) * fy |
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tau_Temp(6) = tau_Temp(6) - d(2) * fz |
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tau_Temp(7) = tau_Temp(7) - d(3) * fx |
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tau_Temp(8) = tau_Temp(8) - d(3) * fy |
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tau_Temp(9) = tau_Temp(9) - d(3) * fz |
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|
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virial_Temp = virial_Temp + & |
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(tau_Temp(1) + tau_Temp(5) + tau_Temp(9)) |
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|
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endif |
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endif |
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|
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endif |
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return |
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|
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end subroutine do_lj_pair |
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|
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|
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!! Calculates the mixing for sigma or epslon |
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|
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function calcLJMix(thisParam,param1,param2,status) result(myMixParam) |
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character(len=*) :: thisParam |
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real(kind = dp) :: param1 |
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real(kind = dp) :: param2 |
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real(kind = dp ) :: myMixParam |
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|
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integer, optional :: status |
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|
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myMixParam = 0.0_dp |
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|
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if (present(status)) status = 0 |
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select case (LJ_Mixing_Policy) |
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case (1) |
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select case (thisParam) |
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case ("sigma") |
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myMixParam = 0.5_dp * (param1 + param2) |
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case ("epsilon") |
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myMixParam = sqrt(param1 * param2) |
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case default |
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status = -1 |
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end select |
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case default |
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status = -1 |
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end select |
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end function calcLJMix |
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|
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end module lj |
