The circumflex is formed from the union of the acute and the grave ( = ^), never from . Thus, παῖς πάὶς, εὖ ἔὺ. Similarly, since every long vowel may be resolved into two short units (
a. The whole vowel receives the acute when the second short unit of a vowel long by nature is accented: Δί_ Δὶί.
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].