# write as a module, all but exported function aziz() are hidden from outside,
# they are visible in the local, module's scope only.

module Aziz
export aziz

# He-He Aziz potential
const epsil = 10.9560000
const rm    = 2.96830000
const aa    = 1.86924404e5
const dee   = 1.43800000
const alpha = 10.5717543
const beta  = -2.07758779  
const c6    = 1.35186623
const c8    = 0.41495143
const c10   = 0.17151143


function aziz(r)
    x = r/rm    
    if x < dee
        fx = exp(-(dee/x-1)^2)
    else
        fx = 1
    end 
    V =epsil*(aa*exp(-alpha*x+beta*x^2)-fx*(c6/x^6 + c8/x^8 + c10/x^10))
    return V
end

end