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IMPLICIT NONE
INTEGER, PARAMETER :: dp=KIND(0.0D0)
REAL(KIND=dp) :: res
res=exp_radius_very_extended( 0 , 1 , 0 , 1, &
(/0.0D0,0.0D0,0.0D0/),&
(/1.0D0,0.0D0,0.0D0/),&
(/1.0D0,0.0D0,0.0D0/),&
1.0D0,1.0D0,1.0D0,1.0D0)
if (res.ne.1.0d0) call abort()
CONTAINS
FUNCTION exp_radius_very_extended(la_min,la_max,lb_min,lb_max,ra,rb,rp,&
zetp,eps,prefactor,cutoff) RESULT(radius)
INTEGER, INTENT(IN) :: la_min, la_max, lb_min, lb_max
REAL(KIND=dp), INTENT(IN) :: ra(3), rb(3), rp(3), zetp, &
eps, prefactor, cutoff
REAL(KIND=dp) :: radius
INTEGER :: i, ico, j, jco, la(3), lb(3), &
lxa, lxb, lya, lyb, lza, lzb
REAL(KIND=dp) :: bini, binj, coef(0:20), &
epsin_local, polycoef(0:60), &
prefactor_local, rad_a, &
rad_b, s1, s2
epsin_local=1.0E-2_dp
prefactor_local=prefactor*MAX(1.0_dp,cutoff)
rad_a=SQRT(SUM((ra-rp)**2))
rad_b=SQRT(SUM((rb-rp)**2))
polycoef(0:la_max+lb_max)=0.0_dp
DO lxa=0,la_max
DO lxb=0,lb_max
coef(0:la_max+lb_max)=0.0_dp
bini=1.0_dp
s1=1.0_dp
DO i=0,lxa
binj=1.0_dp
s2=1.0_dp
DO j=0,lxb
coef(lxa+lxb-i-j)=coef(lxa+lxb-i-j) + bini*binj*s1*s2
binj=(binj*(lxb-j))/(j+1)
s2=s2*(rad_b)
ENDDO
bini=(bini*(lxa-i))/(i+1)
s1=s1*(rad_a)
ENDDO
DO i=0,lxa+lxb
polycoef(i)=MAX(polycoef(i),coef(i))
ENDDO
ENDDO
ENDDO
polycoef(0:la_max+lb_max)=polycoef(0:la_max+lb_max)*prefactor_local
radius=0.0_dp
DO i=0,la_max+lb_max
radius=MAX(radius,polycoef(i)**(i+1))
ENDDO
END FUNCTION exp_radius_very_extended
END
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