Alpha factor

The α-factor is used to predict the solid–liquid interface type of a material during solidification.
Method.
According to John E. Gruzleski in his book Microstructure Development During Metalcasting (1996):
α = (L/k*TE)*(η/v)
where 
L is latent heat of fusion
k is Boltzmann’s constant
TE is equilibrium freezing temperature
η is the number of nearest neighbours an atom has in the interface plane
v is the number of nearest neighbours in the bulk solid
Since L/TE = ΔSf
where ΔSf is the molar entropy of fusion of the material
α = ΔSf/k(η/v)
According to Martin Glicksman in his book Principles of Solidification : An Introduction to Modern Casting and Crystal Growth Concepts(2011):
α = ΔSf/Rg(η1/Z)
where Rg is the universal gas constant,
(η1/Z) is similar to previous, always 1/4<(η1/Z)<1