mirror of
https://github.com/QuantumPackage/qp2.git
synced 2024-12-25 04:53:32 +01:00
44 lines
854 B
Fortran
44 lines
854 B
Fortran
|
|
! ---
|
|
|
|
|
|
|
|
subroutine jBH_elem_fct_grad(alpha, r1, r2, fct, grad1_fct)
|
|
|
|
implicit none
|
|
double precision, intent(in) :: alpha, r1(3), r2(3)
|
|
double precision, intent(out) :: fct, grad1_fct(3)
|
|
double precision :: dist, tmp1, tmp2, dist_inv
|
|
|
|
dist = (r1(1) - r2(1)) * (r1(1) - r2(1)) &
|
|
+ (r1(2) - r2(2)) * (r1(2) - r2(2)) &
|
|
+ (r1(3) - r2(3)) * (r1(3) - r2(3))
|
|
|
|
|
|
if(dist .ge. 1d-15) then
|
|
dist_inv = 1.d0/dsqrt( dist )
|
|
dist = dist_inv * dist
|
|
|
|
tmp1 = 1.d0 / (1.d0 + alpha * dist)
|
|
|
|
fct = alpha * dist * tmp1
|
|
tmp2 = alpha * tmp1 * tmp1 * dist_inv
|
|
grad1_fct(1) = tmp2 * (r1(1) - r2(1))
|
|
grad1_fct(2) = tmp2 * (r1(2) - r2(2))
|
|
grad1_fct(3) = tmp2 * (r1(3) - r2(3))
|
|
|
|
else
|
|
|
|
grad1_fct(1) = 0.d0
|
|
grad1_fct(2) = 0.d0
|
|
grad1_fct(3) = 0.d0
|
|
fct = 0.d0
|
|
|
|
endif
|
|
|
|
return
|
|
end
|
|
|
|
! ---
|
|
|