I'm having some trouble pricing a 0% interest rate Floor following Black's formula. The term d1 contains the expresion Ln(Forward/Strike) if the strike is exactly 0 this expresion yields an indetermination and therefore we can't compute N(d1) in the pricing formula.
I was wondering how to work around this. A peer suggested to compute the regular formula using a 100% probability, but the results are not really meningful.
Aside from the displaced model is there any other adjustment to the black model to price a 0% interest rate floor?