where r i is the atomic radius of element i and r ¯ ¯ = ∑ ∑ i = 1 N c i r i . Formation of a solid-solution phase requires a δ ≤ 6.6%, which is an empirical number based on experiments on bulk metallic glasses (BMG). Exception are found on both side of 6.6%: some alloys with 4% < δ ≤ 6.6% do form intermetallics, and solid-solution phase do appear in alloy with δ > 9%