mirror of
https://github.com/QuantumPackage/qp2.git
synced 2024-11-08 06:23:37 +01:00
72 lines
2.8 KiB
Fortran
72 lines
2.8 KiB
Fortran
|
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_at_r_vector(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*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_at_r(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*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
|