added becke_numerical_grid/example.irp.f

src/becke_numerical_grid/example.irp.f

@@ -0,0 +1,71 @@
+subroutine example_becke_numerical_grid
+ implicit none
+ include 'constants.include.F'
+ BEGIN_DOC 
+! subroutine that illustrates the main features available in becke_numerical_grid
+ END_DOC
+ integer :: i,j,k,ipoint
+ double precision :: integral_1, integral_2,alpha,center(3)
+ print*,''
+ print*,'**************'
+ print*,'**************'
+ print*,'routine that illustrates the use of the grid'
+ print*,'**************'
+ print*,'This grid is built as the reunion of a spherical grid around each atom'
+ print*,'Each spherical grid contains a certain number of radial and angular points'
+ print*,''
+ print*,'n_points_integration_angular = ',n_points_integration_angular
+ print*,'n_points_radial_grid         = ',n_points_radial_grid        
+ print*,''
+ print*,'As an example of the use of the grid, we will compute the integral of a 3D gaussian'
+ ! parameter of the gaussian: center of the gaussian is set to the first nucleus
+ center(1:3)=nucl_coord(1,1:3)
+ ! alpha = exponent of the gaussian
+ alpha = 1.d0
+
+ print*,'' 
+ print*,'The first example uses the grid points as one-dimensional array' 
+ print*,'This is the mostly used representation of the grid' 
+ print*,'It is the easyest way to use it with no drawback in terms of accuracy'
+ integral_1 = 0.d0
+ ! you browse all the grid points as a one-dimensional array
+ do i = 1,  n_points_final_grid 
+  double precision :: weight, r(3)
+  ! you get x, y and z of the ith grid point 
+  r(1) = final_grid_points(1,i)
+  r(2) = final_grid_points(2,i)
+  r(3) = final_grid_points(3,i)
+  weight = final_weight_functions_at_final_grid_points(i)
+  double precision :: distance, f_r
+  ! you compute the function to be integrated 
+  distance = dsqrt( (r(1) - center(1))**2 +  (r(2) - center(2))**2 + (r(3) - center(3))**2 )
+  f_r = dexp(-alpha * distance)
+  ! you add the contribution of the grid point to the integral 
+  integral_1 += f_r * weight
+ enddo
+ print*,'integral_1      =',integral_1
+ print*,'(pi/alpha)**1.5 =',(pi / alpha)**1.5
+ print*,''
+ print*,''
+ print*,'The second example uses the grid points as a collection of spherical grids centered on each atom' 
+ print*,'This is mostly useful if one needs to split contributions between radial/angular/atomic of an integral' 
+ ! you browse the nuclei
+ do i = 1, nucl_num
+ ! you browse the radial points attached to each nucleus
+  do j = 1, n_points_radial_grid
+ ! you browse the angular points attached to each radial point of each nucleus
+   do k = 1, n_points_integration_angular
+    r(1) = grid_points_per_atom(1,k,j,i)
+    r(2) = grid_points_per_atom(2,k,j,i)
+    r(3) = grid_points_per_atom(3,k,j,i)
+    weight = final_weight_functions_at_grid_points(k,j,i)
+    distance = dsqrt( (r(1) - center(1))**2 +  (r(2) - center(2))**2 + (r(3) - center(3))**2 )
+    f_r = dexp(-alpha * distance)
+    integral_2 += f_r * weight
+   enddo
+  enddo
+ enddo
+ print*,'integral_2      =',integral_2
+ print*,'(pi/alpha)**1.5 =',(pi / alpha)**1.5
+ print*,''
+end

src/becke_numerical_grid/grid_becke.irp.f

@@ -158,7 +158,6 @@ BEGIN_PROVIDER [double precision, weight_functions_at_grid_points,   &
         enddo
         accu = 1.d0/accu
         weight_functions_at_grid_points(l,k,j) = tmp_array(j) * accu
-!       print*,weight_functions_at_grid_points(l,k,j)
       enddo
     enddo
   enddo