get_polarizibilities Subroutine

subroutine get_polarizibilities(self, mol, gwvec, gwdcn, gwdq, alpha, dadcn, dadq)
   !DEC$ ATTRIBUTES DLLEXPORT :: get_polarizibilities

   !> Instance of the dispersion model
   class(d4s_model), intent(in) :: self

   !> Molecular structure data
   class(structure_type), intent(in) :: mol

   !> Pairwise weighting function for the atomic reference systems
   real(wp), intent(in) :: gwvec(:, :, :)

   !> Derivative of the pairwise weighting function w.r.t. the coordination number
   real(wp), intent(in), optional :: gwdcn(:, :, :)

   !> Derivative of the pairwise weighting function w.r.t. the partial charge
   real(wp), intent(in), optional :: gwdq(:, :, :)

   !> Static polarizibilities for all atoms.
   real(wp), intent(out) :: alpha(:)

   !> Derivative of the polarizibility w.r.t. the coordination number
   real(wp), intent(out), optional :: dadcn(:)

   !> Derivative of the polarizibility w.r.t. the partial charge
   real(wp), intent(out), optional :: dadq(:)

   integer :: iat, izp, iref
   real(wp) :: refa, da, dadcni, dadqi

   if (present(gwdcn).and.present(dadcn) &
      & .and.present(gwdq).and.present(dadq)) then
      alpha(:) = 0.0_wp
      dadcn(:) = 0.0_wp
      dadq(:) = 0.0_wp

      !$omp parallel do default(none) schedule(runtime) &
      !$omp shared(alpha, dadcn, dadq, mol, self, gwvec, gwdcn, gwdq) &
      !$omp private(iat, izp, iref, refa, da, dadqi, dadcni)
      do iat = 1, mol%nat
         izp = mol%id(iat)
         da = 0.0_wp
         dadcni = 0.0_wp
         dadqi = 0.0_wp
         do iref = 1, self%ref(izp)
            refa = self%aiw(1, iref, izp)
            da = da + gwvec(iref, iat, iat) * refa
            dadcni = dadcni + gwdcn(iref, iat, iat) * refa
            dadqi = dadqi + gwdq(iref, iat, iat) * refa
         end do
         alpha(iat) = da
         dadcn(iat) = dadcni
         dadq(iat) = dadqi
      end do

   else

      alpha(:) = 0.0_wp

      !$omp parallel do default(none) schedule(runtime) &
      !$omp shared(alpha, mol, self, gwvec) private(iat, izp, iref, refa, da)
      do iat = 1, mol%nat
         izp = mol%id(iat)
         da = 0.0_wp
         do iref = 1, self%ref(izp)
            da = da + gwvec(iref, iat, iat) * self%aiw(1, iref, izp)
         end do
         alpha(iat) = da
      end do
   end if

end subroutine get_polarizibilities