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quack/src/utils/norm_coeff.f90

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2019-03-20 13:38:42 +01:00
function norm_coeff(alpha,a)
implicit none
! Input variables
double precision,intent(in) :: alpha
integer,intent(in) :: a(3)
! local variable
double precision :: pi,dfa(3),dfac
integer :: atot
! Output variable
double precision norm_coeff
pi = 4d0*atan(1d0)
atot = a(1) + a(2) + a(3)
dfa(1) = dfac(2*a(1))/(2d0**a(1)*dfac(a(1)))
dfa(2) = dfac(2*a(2))/(2d0**a(2)*dfac(a(2)))
dfa(3) = dfac(2*a(3))/(2d0**a(3)*dfac(a(3)))
norm_coeff = (2d0*alpha/pi)**(3d0/2d0)*(4d0*alpha)**atot
norm_coeff = norm_coeff/(dfa(1)*dfa(2)*dfa(3))
norm_coeff = sqrt(norm_coeff)
end function norm_coeff