2016-04-17 23:30:04 +02:00
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double precision function step_function_becke(x)
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implicit none
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double precision, intent(in) :: x
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double precision :: f_function_becke
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integer :: i,n_max_becke
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2016-07-16 16:09:50 +02:00
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!if(x.lt.-1.d0)then
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! step_function_becke = 0.d0
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!else if (x .gt.1)then
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! step_function_becke = 0.d0
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!else
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step_function_becke = f_function_becke(x)
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!!n_max_becke = 1
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do i = 1, 4
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step_function_becke = f_function_becke(step_function_becke)
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enddo
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step_function_becke = 0.5d0*(1.d0 - step_function_becke)
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!endif
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2016-04-17 23:30:04 +02:00
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end
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double precision function f_function_becke(x)
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implicit none
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double precision, intent(in) :: x
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f_function_becke = 1.5d0 * x - 0.5d0 * x*x*x
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end
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double precision function cell_function_becke(r,atom_number)
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implicit none
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double precision, intent(in) :: r(3)
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integer, intent(in) :: atom_number
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BEGIN_DOC
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! atom_number :: atom on which the cell function of Becke (1988, JCP,88(4))
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! r(1:3) :: x,y,z coordinantes of the current point
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END_DOC
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double precision :: mu_ij,nu_ij
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double precision :: distance_i,distance_j,step_function_becke
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integer :: j
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distance_i = (r(1) - nucl_coord_transp(1,atom_number) ) * (r(1) - nucl_coord_transp(1,atom_number))
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distance_i += (r(2) - nucl_coord_transp(2,atom_number) ) * (r(2) - nucl_coord_transp(2,atom_number))
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distance_i += (r(3) - nucl_coord_transp(3,atom_number) ) * (r(3) - nucl_coord_transp(3,atom_number))
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distance_i = dsqrt(distance_i)
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cell_function_becke = 1.d0
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do j = 1, nucl_num
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if(j==atom_number)cycle
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distance_j = (r(1) - nucl_coord_transp(1,j) ) * (r(1) - nucl_coord_transp(1,j))
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distance_j+= (r(2) - nucl_coord_transp(2,j) ) * (r(2) - nucl_coord_transp(2,j))
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distance_j+= (r(3) - nucl_coord_transp(3,j) ) * (r(3) - nucl_coord_transp(3,j))
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distance_j = dsqrt(distance_j)
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mu_ij = (distance_i - distance_j)/nucl_dist(atom_number,j)
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nu_ij = mu_ij + slater_bragg_type_inter_distance_ua(atom_number,j) * (1.d0 - mu_ij*mu_ij)
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cell_function_becke *= step_function_becke(nu_ij)
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enddo
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end
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